Resumo em Inglês:

ABSTRACT Friction Stir Welding (FSW) is a solid-state joining technique which attained significant awareness due to its ability to produce high-quality welds without melting the base materials. The distribution of temperature across the plates during the FS Welding process is critical for determining the microstructural evolution, mechanical properties, and residual stresses of the welded joints. This research article aims to develop a comprehensive finite element (FE) model to predict the temperature distribution during the FS Welding process. The FE model incorporates the coupled thermo-mechanical behaviour of the FS Welding process, considering the heat generation and temperature-dependent material characteristics, plastic deformation and friction, and also the effect of tool geometry. The model is validated using experimental measurements, and the results obtained shows the simulated values representing the highest temperature obtained with respect to experimental values are within an error percentage of 3% from the experimental values and thereby validating the FEA procedure.

Resumo em Inglês:

ABSTRACT This study investigates the mechanical properties of Flux Core Arc Welded (FCAW) Duplex Stainless Steel (DSS) under various welding modes: Constant Current (CC), Pulsed Current (PC), and Surface Tension Transfer (STT). Results indicate that the STT mode of FCAW delivers optimal mechanical properties, with yield strengths ranging from 711 MPa to 743 MPa and ultimate strengths from 758 MPa to 842 MPa. In comparison, CC mode yielded slightly lower results with yield strengths of 766 MPa to 781 MPa and ultimate strengths of 890 MPa to 901 MPa, while PC mode showed intermediate values. Impact strength analysis across CC, PC, and STT modes reveals that STT welds absorb the highest energy, ranging from 47 J to 48 J in the weld metal and 50 J to 74 J in the HAZ, compared to CC (20 J to 28 J) and PC (24 J to 38 J) modes. Fractographic analysis using Scanning Electron Microscopy (SEM) confirms uniform surface properties and minimal defects in STT mode welds, indicating improved weld integrity. Vickers hardness testing demonstrates higher values in the Heat Affected Zone (HAZ) near the weldment for STT mode (up to 300.27 HV), suggesting superior strength characteristics.

Resumo em Português:

RESUMO Uma maneira eficaz de se aproveitar os resíduos agrícolas é convertê-los na forma de carvão ativado, o qual possui diversas utilidades, incluindo a purificação de água. Com este objetivo o carvão ativado derivado do caroço de manga (Mangifera indica L.) foi utilizado como adsorvente para a remoção de íons chumbo presentes em soluções aquosas preparadas. A manga foi lavada, seca e teve seu caroço removido para ser preparado como carvão, através da pirolise s 400°C, seguido da ativação com H2SO4 1:1 (v/v) por 12 horas e lavagem do material para liberar os poros do material. O processo de adsorção foi realizado em batelada, introduzindo 30 mL de solução de Pb(II) 50 mg L-1 e uma determinada massa do carvão em tubos cônicos com tampa, submetidos a agitação orbital. Após o tempo estabelecido o adsorvente foi separado por filtração e o teor de Pb(II) restante no filtrado foi feita a determinação no FAAS. Os estudos mostraram uma remoção de 90% na concentração de Pb(II). O adsorvente proposto mostrou-se eficiente para remoção de Pb(II) em soluções aquosas, sendo viável sua aplicação no tratamento de efluentes químicos aquosos.

Resumo em Inglês:

ABSTRACT An effective way to utilize agricultural waste is to convert it into the activated form, which has several uses, including water purification. With this objective, activated carbon derived from mango seeds (Mangifera indica L.) was used as an adsorbent to remove lead ions present in prepared aqueous solutions. The mango was washed, dried and had its core removed to be prepared as charcoal, through pyrolysis at 400°C, followed by activation with H2SO4 1:1 (v/v) for 12 hours and washing the material to release the pores of the material. The adsorption process was carried out in batch, introducing 30 mL of Pb(II) solution 50 mg L-1 and a certain mass of charcoal into conical tubes with lids, subjected to orbital agitation. After the established time, the adsorbent was separated by filtration and the Pb(II) content remaining in the filtrate was determined using the FAAS. Studies showed a 90% removal in Pb(II) concentration. The proposed adsorbent proved to be efficient for removing Pb(II) in aqueous solutions, making its application viable in the treatment of aqueous chemical effluents.

Resumo em Português:

RESUMO A manufatura aditiva (AM) é utilizada para a otimização do processo produtivo, em especial, para a fabricação de peças com geometrias complexas. Dentre as diversas técnicas de AM, a Fusão Seletiva a Laser (FSL) é uma das mais utilizadas. Diversas ligas podem ser empregadas nesse tipo de processo produtivo. A liga Ti6Al4V é amplamente utilizada por reunir um gama de características que permitem a aplicação em várias áreas. As ligas Ti α + β são largamente utilizadas na indústria aeroespacial, na área médica e odontológica. O rápido resfriamento a partir de múltiplos ciclos de fusão/refusão resultam em transformações de fases adifusionais na microestrutura produto da FSL na liga Ti6Al4V, ou seja, promovem a formação da fase α’ martensítica e retenção da fase β. O objetivo do presente trabalho foi avaliar a influência na microestrutura dos pós-tratamentos térmicos de recozimento (850 e 1050 ºC durante 90 min resfriado no forno) da liga Ti6Al4V processada por FSL. A microestrutura da liga foi caracterizada por microscopia óptica (MO), eletrônica de varredura (MEV) com uso do detector de elétrons secundários (SE), como também a evolução composicional das fases presentes por espectroscopia de raios X por energia dispersiva (EDS) no MEV. Os resultados mostraram que o tratamento térmico a 850 ºC (encharque na zona intercrítica) não promoveu significativa reversão da martensita α’ e a microestrutura composta de α’ + β manteve-se muito próxima a como processada na FSL, como também a composição elementar das fases não se alterou. Por outro lado, com o tratamento térmico a 1050 ºC (com encharque no campo de estabilidade da fase β) verificou-se a completa reversão da martensita α’, em função de pós resfriamento observar-se tão somente as fases α + β, além da repartição do soluto V pelo enriquecimento deste na fase β e subsequente empobrecimento na fase α.

Resumo em Inglês:

ABSTRACT Additive production (AM) is used to optimize the production process, in particular, for the manufacture of parts with complex geometries. Among the various AM techniques, Selective Laser Melting (SLM) is one of the most used. Several alloys can be used in this type of manufacturing process. The Ti6Al4V alloy is widely used to bring together a range of characteristics that allow application in different areas. The Ti α + β alloys are widely used in the aerospace industry, medical and dental fields. The rapid cooling from melting/remelting multiple cycles resulting in diffusionless phase transformation on the Ti6Al4V SLM product, in other words promote the α’ martensitic phase formation. The objective of the present work was to evaluate the influence on the microstructure of the annealing post-treatments (850 and 1050 ºC for 90 min with cooling on furnace) of the Ti6Al4V alloy processed by SLM. The microstructure of the alloy was characterized by optical (OM) and scanning electron microscopy (SEM) using a secondary electron (SE) detector, as well as the compositional evolution of the phases present by X-ray energy dispersive spectroscopy (EDS). The results demonstrated that heat treatment at 850 ºC (with soaking on the intercritical zone) did not promote significant reversion of the α’ martensite and the microstructure composed of α’ + β remained very close to that processed in SLM, as well as the elemental composition of the phases did not change. On the other hand, with heat treatment at 1050 ºC (with soaking on the β phase stability field) the complete reversion of the α’ martensite was verified, due to post-cooling only the α + β phases were observed, in addition to the V solute partition due to its enrichment in the β phase and subsequent impoverishment in the α phase.

Resumo em Inglês:

ABSTRACT Tunneling over a field leads to surface, subsurface settlement, and lateral deformation. Tunnels built to nearby foundations of building, produces a ground loss, which affects the foundation behavior. This paper aimed to study the displacement behavior of existing pile foundations in the sandy ground during tunnel excavation using the numerical software PLAXIS 3D. The comparison of published results from various numerical analysis software was used to verify the validity of the PLAXIS 3D approach. However, the uncertainties of material properties of soil in satisfying the parameters of the Mohr-Coulomb model were assumed in the analyses. Both single pile and pile group effects due to tunneling are analyzed. A total of 21 FE analyses were involved in predicting the regular plane strain responses of piles such as lateral displacement and vertical displacement identified during the excavation process of tunneling. The parametric research on pile and pile group responses involved the study of the effect of relative density, pile location from tunnel centerline, pile diameter, pile length, and volume loss. Based on the safe limiting value of lateral and vertical displacement as 5 mm and 10 mm respectively, recommendations for the tunnel's location concerning the adjacent existing piles were provided.

Resumo em Inglês:

ABSTRACT This experimental study investigates the structural performance of reinforced concrete (RC) beams retrofitted with Glass Fiber-Reinforced Polymer (GFRP) composites. Retrofitting existing concrete structures has gained attention as an environmentally and economically viable method to enhance load-bearing capacity and extend lifespan. The study involves comprehensive experiments on RC beams with GFRP composites to improve the structural behavior of deteriorated or under-designed beams. RC beams representing common structural configurations, such as those with insufficient flexural capacity or corrosion, were fabricated. GFRP retrofitting involved applying sheets or strips to the tension and shear faces to enhance flexural strength and ductility. Parameters included the number of GFRP layers, their orientation, and bonding methods. Performance variables like load-carrying capability, deflection, cracking patterns, and failure modes were meticulously monitored. The research also explored the impact of GFRP retrofitting on environmental resistance and long-term endurance. Results are expected to provide insights into the effectiveness of GFRP composites for RC beam retrofitting, offering practical guidelines for engineers and researchers in rehabilitating and strengthening concrete structures, and advancing sustainable solutions for aging infrastructure.

Resumo em Português:

RESUMO O presente trabalho objetivou avaliar o desempenho de algoritmos de aprendizado de máquinas na predição da resistência à compressão de argamassas. A base de dados foi criada através de uma busca bibliográfica de mais de 50 referências que foram catalogadas para conter dados de dosagens de argamassa com ou sem adição de resíduos de construção e demolição (RCD). O conjunto de dados avaliado passou por um pré-processamento de integração dos dados de resíduo de construção e demolição, e normalização. Como normalização optou-se pelo uso da técnica z-score. Em seguida, os algoritmos de Aprendizado de Máquina (AM): regressões linear e polinomial, árvores de decisão, ensembles e redes neurais foram utilizados para a predição da resistência à compressão. O conjunto de dados foi separado em 80% para treino e validação e 20% para teste. A validação cruzada empregada foi do tipo k-fold com 10 divisões no subconjunto de treino. Avaliando o desempenho dos modelos o algoritmo tipo ensemble Gradient Boosting apresentou o melhor desempenho quando comparado aos demais, atingindo um valor superior a 90% no coeficiente de determinação. Por fim, conclui-se que o AM é uma ferramenta prática importante na predição da resistência à compressão de argamassas. Além disso, o modelo de inteligência artificial foi prototipado para uso da comunidade científica e técnica em uma versão web disponível através do framework Streamlit da linguagem Python.

Resumo em Inglês:

ABSTRACT The present work aimed to evaluate the performance of machine learning algorithms in predicting the compressive strength of mortars. The database was created through a bibliographic search of more than 50 references that were cataloged to contain data on mortar dosages with or without the addition of construction waste. The dataset used in the experiments underwent preprocessing, which included the integration of construction and demolition waste data and normalization. For normalization, the z-score technique was chosen. Then, the algorithms, linear regressions, decision trees, ensembles, and neural networks were used to predict compressive strength. The dataset was separated into 80% for training and validation and 20% for testing. The cross-validation was of the k-fold type with ten divisions in the training subset. Evaluating the performance of the models, the ensemble Gradient Boosting algorithm showed the best performance when compared to the others, reaching a value greater than 89% in the coefficient of determination. Finally, it is concluded that Machine Learning (ML) is a practical calculation tool for predicting the compressive strength of mortars. Furthermore, the artificial intelligence model was prototyped for the scientific and technical community use in a web version available through the Python Streamlit framework.

Resumo em Inglês:

ABSTRACT The over-exploitation of river sand for construction has led to significant environmental concerns, prompting bans and the search for viable alternatives such as Manufactured Sand (M-Sand). This study evaluates the feasibility of M-Sand as a substitute for river sand in concrete production by comparing their physical, mechanical, and durability properties. Physical property assessments include grading and specific gravity. Mechanical properties such as compressive and split tensile strengths were evaluated to determine the structural integrity of the concrete. Durability tests, including the Rapid Chloride Penetration Test (RCPT), alkalinity test, and impact resistance test, were conducted to assess the concrete’s resilience to environmental challenges. This study investigated M20, M25, and M30 grades of concrete using river sand and M-Sand. Compressive strengths for M-Sand were slightly lower than river sand but remained within acceptable ranges: 23.80 N/mm2 (M20), 27.50 N/mm2 (M25), and 33.85 N/mm2 (M30). Split tensile strengths followed a similar trend. Durability tests, including RCPT, showed comparable resistance to chloride penetration, with all mixes rated “Very Low.” Alkalinity levels were maintained between 9 and 12, protecting steel reinforcement. Impact resistance and ductility were also comparable, with an average ductility index of 1.289. M-Sand is confirmed as a sustainable alternative to river sand.

Resumo em Inglês:

ABSTRACT In turning, the interaction among target material tool and chip usually causes thermal damage as well as tool wear. High-pressure coolant is an emerging technology that delivers and the tool interface region. High coolant pressure allows better penetration of coolant by enhancing the lubrication effect, and decreasing thermal damage and tool wear through cooling effect at the cutting zone. The manufacturing sector wants to create a lot of goods in a short amount of time as the fourth industrial revolution approaches. Response surface design and the Taguchi L27 orthogonal array methodological paradigm are used in this work. The cutting speed (750, 1000, 1250 rpm), feed rate (0.075, 0.1, 0.125 mm/rev), depth of cut (0.25, 0.50, 0.75 mm), and fluid pressure (2.5, 5, 7.5 bar) represent as the process parameters. The objective of this paper, is to investigate how the surface finish, cutting force, and tool wear mechanism are influenced by coolants under the different coolant pressure, depth of cut, feed and speed in turning of monel using coated carbide tool. Also in this work the performance of cutting coolant (CuO and graphene) were compared with respect to tool wear, cutting force, surface roughness, cutting zone temperature chip morphology and surface modification during turning of monel. The findings showed that, under extreme wear conditions, GO-based nano fluids improved machining performance, as measured by increased cooling and lubrication regime, cutting temperature of 122 °C, and surface roughness of 0.0462 µm and flank wear of 0.2 mm.

Resumo em Inglês:

ABSTRACT Tapioca Peel Ash (TPA), a plentiful agricultural residue, demonstrates potential as a Supplementary Cementitious Material (SCM) in concrete. This research intends to maximize the efficiency of TPA integration through the Central Composite Design (CCD) approach to ascertain the optimal mix of components for enhanced performance. The physicochemical analysis assessed TPA’s pozzolanic properties. Laboratory tests analyzed the compressive and flexural strengths of concrete mixes containing various amounts of TPA, cement, and aggregates. The outcomes showed that a mixture ratio of 0.2:0.0875:0.3625:0.4625 (Cement : TPA : Fine Aggregate : Coarse Aggregate) achieved an ultimate compressive strength of 27.08 MPa. Moreover, a ratio of 0.2:0.0875:0.3625:0.525 yielded a maximum flexural strength of 9.84 MPa. Quadratic predictive models and statistical analyses were derived to determine the ideal concrete mixture that substantially improves compressive and flexural strengths. Validation via student’s t-test showed a significant correlation between experimental and simulated values, with p-values of 0.9987 and 0.9912 for compressive and flexural strengths, respectively. This research highlights the opportunity to improve concrete properties and minimize waste by effectively using TPA in construction.

Resumo em Português:

RESUMO As adutoras de abastecimento de água estão constantemente susceptíveis a corrosão, por agentes internos e externos, causando fissuras e rupturas das estruturas, ocasionando prejuízos econômicos e ambientais. Os processos que causam corrosão são químicos ou eletroquímicos, resultando na oxidação do material na presença de substâncias que sofrem redução, o que degrada suas propriedades químicas, físico-químicas ou mecânica. Uma alternativa para prevenir ou retardar o processo corrosivo, é a utilização de inibidores naturais em revestimentos para proteção contra a corrosão. Propõe-se o uso de inibidores naturais, como o extrato glicólico de Aloe Vera, para mitigar a corrosão. O estudo avaliou o desempenho desse inibidor por meio de ensaios eletroquímicos, perda de massa e análise de espectroscopia no infravermelho por transformada de Fourier - IVTR do extrato. Resultados indicam que a concentração do Bioinibidor de Aloe Vera em 0,3 ml apresentou melhor eficiência de 45,05%, com redução na taxa de corrosão de 31,84% nos ensaios de perda de massa, em relação as demais concentrações. A análise IVTR revelou grupos funcionais (OH; C-H; C=C) no extrato associados às propriedades inibitórias. Conclui-se que o extrato de Aloe Vera tem potencial como inibidor de corrosão para ferro fundido dúctil.

Resumo em Inglês:

ABSTRACT Water supply pipelines are constantly susceptible to corrosion from internal and external agents, causing cracks and ruptures in the structures, leading to economic and environmental damages. The processes that cause corrosion are either chemical or electrochemical, resulting in the oxidation of the material in the presence of substances that undergo reduction, which degrades its chemical, physicochemical, or mechanical properties. One alternative to prevent or delay the corrosion process is the use of natural inhibitors in coatings for corrosion protection. The use of natural inhibitors, such as the glycol extract of Aloe vera, is proposed to mitigate corrosion. This study evaluated the performance of this inhibitor through electrochemical tests, mass loss, and Fourier Transform Infrared Spectroscopy (FTIR) analysis of the extract. Results indicate that the concentration of 0.3 mL of the Aloe vera Bioinhibitor showed the best efficiency at 45.05%, with a reduction in the corrosion rate of 31.84% in mass loss tests compared to other concentrations. FTIR analysis revealed functional groups (OH; C-H; C=C) in the extract associated with inhibitory properties. It is concluded that the Aloe vera extract has potential as a corrosion inhibitor for ductile cast iron.

Resumo em Inglês:

ABSTRACT Problem: The contamination of water bodies by copper (II) ions caused by industries harms the environment and human health. Solution: Adsorption removes such ions using activated carbon, which may be replaced with bioadsorbents (biomass from agro-industrial waste), as they are more accessible and renewable, capturing contaminant species from functional groups. This study verified the adsorption efficiency of copper (II) ions using mango residue flour (Mangifera indica L., MRF) as a bioadsorbent. Methodology: MRF preparation consisted of drying Tommy mango pits and seeds (80°C, 48 hours), crushing, sieving, and treating them with hydrochloric acid (0.05 mol L–1, 10 minutes). The MRF characterization techniques were FTIR and point of zero charge (PZC). Adsorption studies occurred at 25°C, pH of 4.6, and constant stirring. Adsorption time and MRF mass were the parameters to determine optimal adsorption conditions. Complexometric titration determined the concentration of adsorbed copper (II) ions. Results and discussion: FTIR identified the functional groups interacting with copper (II) ions. PZC determined that the surface charge of MRF is neutral at a pH of 4.3, positive and interacting with anions at a pH lower than 4.3, and negative and interacting with cations at a pH higher than 4.3. The optimal adsorption conditions were 30 minutes and 0.1 g of MRF. The non-linear Redlich-Peterson and Langmuir isotherm models provided the best fits, suggesting a multilayer MRF adsorption mechanism. The maximum percentage of copper (II) ion removal was 77.5%. Conclusion: Adsorption using MRF potentially removes copper (II) ions.

Resumo em Inglês:

ABSTRACT Sisal fibre reinforced epoxy composites are the subject of this study, which intends to evaluate the influence of fibre orientation on the interlaminar shear strength and thermal parameters of these composites. When it comes to defining the mechanical and thermal performance of natural fibre reinforced polymer composites, the orientation of the fibres is a significant factor, as established by the examination of the current literature. There have been observations that the overall qualities of the composite can be improved by the hybridisation of sisal fibre with other reinforcements, such as glass or carbon fibres. Insights into the ideal fibre orientation that can maximise the interlaminar shear strength and thermal stability of the sisal fibre reinforced epoxy composites are anticipated to be provided by the result of the experimental investigation. Due to the influence of sisal fibre orientations such as 0/90°, 90°, and ± 45° orientation, an experimental investigation was carried out in order to assess the ILSS and thermal property of the material. According to the findings of this research, the orientation 90° demonstrates superior ILSS of 5.531MPa and thermal property 0.396 W/m*K of in comparison to the orientations 0/90° and ± 45° for the same purpose.

Resumo em Inglês:

ABSTRACT Friction stir welding (FSW) offers a solid-state solution for joining materials that are challenging to weld using conventional methods, addressing issues like aluminium oxidation typically encountered in fusion welding. This study focused on FSW of dissimilar aluminium alloys AA5754 and AA6061, investigating mechanical properties such as Vickers hardness and ultimate tensile strength. Welding parameters were optimized using a mathematical model based on a central composite design, highlighting their significant impact on output responses. Of particular concern in dissimilar alloy welding is the formation of intermetallic compounds at the alloy interface, which can detrimentally affect mechanical properties and corrosion resistance of the weld joint. Therefore, characterizing the types, distribution, and thickness of these compounds through advanced analytical techniques such as electron microscopy and X-ray diffraction will be an integral part of this study. Moreover, the practical implications of using FSW for joining dissimilar aluminium alloys AA5754 and AA6061 will be discussed. This includes its potential applications in industries where lightweight structures with high mechanical performance are required. ANOVA and RSM were used for accurate and best outcomes. The best process parameters were found to be 100% boron carbide reinforcement, 70 mm/min traverse speed, and 1300 rpm tool rotation speed for improving the mechanical properties of welded connections. Through FSW weldability and performance demonstration of AA5754-AA6061 joints, this research intends to provide important insights on how to extend the use of aluminium alloys in many industrial sectors.

Resumo em Inglês:

ABSTRACT In recent days, sustainable development gained momentum in the construction sector. The present work is to develop an artificial neural network (ANN) to predict chloride diffusivity in concrete. The mix proportions are prepared by varying the processed recycled concrete aggregate (PRCA) percentage. The RCPT (chloride diffusivity) experiment is conducted on concrete specimens with varying percentages of RCPA 10%, 20%, 30%, 40%, and 50%. After several investigations on input parameters, optimal ANN network architecture was found to be a 4-1-3-1 model with high predictive capability, and corresponding R2 values were found to be greater than 0.90 during both training and testing. The experiment reveals that a higher percentage of PRCA replacement leads to higher chloride diffusivity and the same trend is shown in the optimal ANN model. This confirms the accuracy of the current developed ANN network. The ANN a robust tool for optimizing concrete mix designs, ensuring quality control, and promoting sustainable construction practices. The ANN models in predicting chloride diffusivity facilitate the balance between sustainability and durability of concrete structures. Future work aims to expand the dataset with various percentages of PRCA and validate the model's applicability to a wide range of recycled aggregates and environmental conditions.

Resumo em Inglês:

ABSTRACT The unique properties of Inconel 625 make it desirable for engineering applications. It is expensive and complex to machine Inconel 625 due to its unique properties. In light of the widespread use of turned components in crucial aircraft engines, the turning method was chosen to evaluate the impact of turning parameters on cutting forces, surface roughness, material removal rate and temperature. In this study, the Taguchi optimization approach is applied to optimize cutting parameters with laser textured tungsten carbide with HBN nano particle filled cutting tools during high-speed turning of Inconel 625. The cutting parameters include the depth of cut, feed rate, and speed at which the work piece is turned. ANOVA was used to identify the most influencing process parameters on the turning operation. The cutting speed of 14 m/min, Feed rate of 0.3 mm/rev and depth of cut of 0.33 mm gave a better cutting force of 239 N and material removal rate of 3.22 mm3/min and also a reduced surface roughness to 2.834 µm, and temperature of 61°C. From ANOVA, feed rate 77.38% was identified the most influencing process parameter on the turning operation followed by cutting speed 8.65% and depth of cut 0.41%.

Resumo em Inglês:

Abstract In the quest to enhance filtration system performance and remove microscopic particles, researchers are increasingly interested in affordable materials made from renewable sources with low environmental impact. Cellulose stands out as one of the most promising materials due to its abundance in nature. In this study, we present a simple approach to manufacture cellulose foam with a microfibrillated cellulose (MFC) interface, intended to be used as a filter to capture airborne microparticles. Four different methods were employed to produce the membranes, aiming to analyze and compare the effectiveness of each process, including two distinct solvent exchange approaches and two solvent filtration techniques. Specifically, two membrane production methods were explored: (i) using water as a solvent, and (ii) employing acetone as a solvent. Regarding the solvent filtration process, two modalities were investigated: (i) natural filtration, and (ii) vacuum filtration. The MFC acted as reinforcement, promoting the formation of cross-links between the cellulose pulp fibers, thereby enhancing cellulose interfibrillar cohesion. An experimental system was utilized to assess pressure drop in a gas flow, and filter permeability was calculated. Overall, the membranes exhibited high permeability constants, emerging as a promising material for filtration processes.

Resumo em Inglês:

ABSTRACT This experimental and theoretical study investigated the efficiency of radiation absorption by Cerrobend alloy with varying concentrations of B4C compound. Four blocks were prepared containing 0%, 5%, 10%, and 15% B4C, respectively. The study examined radiation attenuation characteristics, including the mass attenuation coefficient, linear attenuation coefficient, half-value layer thickness, and mean free path, as well as radiobiological consequences for each block, using photon energies of 6 and 15 MeV. It has been observed that the rise in the quantity of B4C leads to a decrease in the material’s ability to absorb photons. The highest mass attenuation coefficient at 6 MeV energy was S1 with 0.0432 cm2/g. The half-value layer of samples S2 and S3 exhibited a larger magnitude compared to samples S1. The tenth-value layer findings obtained with photons with 15 MeV energy were S0 < S1 < S2 < S3. In the experiments with photons with 6 MeV energy, the mean free path value of sample S1 was relatively lower than other samples. The experimental results were consistent with the data obtained from GAMOS and XCOM. Experiments and theoretical studies have shown that the Cerrobend alloy’s photon absorption properties are very similar to those of pure Cerrobend when it is doped with 5 wt% B4C.

Resumo em Português:

RESUMO Este trabalho se insere no contexto de análise de imagens, visando a extração automática de informações complexas com alta precisão. Este estudo teve como objetivo avaliar o desempenho de redes neurais convolucionais na classificação de imagens de concreto em duas classes: (a) não fissuradas e (b) fissuradas. Para tanto, foram empregadas as redes profundas VGG16, VGG19 e ResNet50 com aprendizagem por transferência por meio de ajuste fino. As redes foram treinadas novamente e testadas usando um banco de dados de 40.000 imagens. Após o treinamento, as redes foram testadas, alcançando uma precisão impressionante entre 99,27% e 99,78%. Este alto nível de precisão inspira confiança no uso destes modelos preditivos. Para avaliar a robustez dos modelos, foram gerados gradientes visuais dos pontos focais de atenção das redes nas imagens, mostrando que os modelos focam e capturam aspectos das fotos que realmente caracterizam as fissuras. Com base nos resultados, pode-se concluir que as redes neurais convolucionais são eficazes na classificação de problemas envolvendo concreto e podem ser aplicadas em inspeções precisas para auxiliar engenheiros com alta confiabilidade quanto aos resultados.

Resumo em Inglês:

ABSTRACT This paper is inserted in the context of image analysis, aiming at the automatic extraction of complex information with high precision. This study aimed to evaluate the performance of convolutional neural networks in classifying concrete images into two classes: (a) non-cracked and (b) cracked. For this purpose, VGG16, VGG19, and ResNet50 deep networks were employed with transfer learning through fine-tuning. The networks were re-trained and tested using a database of 40,000 images. After training, the networks were tested, achieving an impressive accuracy between 99.27% and 99.78%. This high accuracy level inspires confidence in using these predictive models. To assess the robustness of the models, visual gradients of the networksʼ attention focal points on the images were generated, showing that the models focus on and capture aspects of the photos that truly characterize the cracks. Based on the results, it can be concluded that convolutional neural networks are effective in classification problems involving concrete and can be applied in accurate inspections to assist engineers with high reliability regarding the results.

Resumo em Inglês:

ABSTRACT Inhaling dust can lead to respiratory diseases, and dust accumulation in the workplace can pose fire and explosion hazards. Traditional dust removal nozzles require high water pressure and produce large droplet diameters. The Laval nozzle, utilizing a converging-diverging section to accelerate fluid to supersonic speeds, achieves finer droplets and a more concentrated particle size distribution. However, curved Laval nozzle is different to manufacture. To study the effect of water pressure on the atomization performance of a Linear Laval nozzle, a laser particle analyzer and a camera were used to test the droplet size and atomization angle. These results were compared with numerical analysis. The findings indicate that as the water pressure increases from 0.1 MPa to 0.5 MPa, the dropletsʼ Sauter Mean Diameter (SMD) increases almost linearly. At the same time, the spray angle tends to decrease. Both experimental and numerical analyses show the same trend. At a water pressure of 0.1 MPa, the atomization performance of the Linear Laval nozzle is optimal. Compared to traditional nozzles, the water pressure is significantly reduced, and the D(3,2) droplet diameter is notably smaller. Moreover, the atomization angle is considerably increased. The spray effect has been significantly improved.

Resumo em Inglês:

Abstract The effect of temperature on tensile and cyclic deformation is studied on SAE 1045 and SAE 4140 commercial steels. Tensile and low cycle fatigue (LCF) tests were performed at room temperature and 250°C. For a temperature of 250°C, an induction heating system was used during the tests. The temperature of the specimen was homogenized 600 s before testing. The tension-compression LCF tests were carried out at total strain amplitudes of ± 0.6%, ± 0.8%, and ± 1.0%. The Coffin-Manson-Basquim model was used to predict the LCF properties of steels. Scanning electron microscopy was used to evaluate the microstructure and the fracture surface. The fracture surfaces of samples tensile tested at room temperature and 250°C were similar. For fatigue testing, the surfaces obtained were also similar with regions of fatigue crack initiation and propagation, and rupture. A crack initiation near the surface was observed for the LCF specimens. Dynamic strain aging and recovery influenced the tensile and fatigue results, for example, the number of reversals to failure decreased for the fatigue test performed at 250°C. For fatigue tests performed at strain of 0.6% in the SAE 1045, the stress increased by 65% at 250°C when compared to testing at room temperature. Consequently, the number of reversals was reduced by 58%.

Resumo em Português:

RESUMO A segurança estrutural de edifícios históricos exige uma análise estrutural avançada. A argamassa geralmente apresenta composição e comportamento estrutural complexos. Em diferentes partes do mundo, existe uma quantidade significativa de construções históricas utilizando argamassas de cal aérea. A umidade em estruturas de cal tem uma influência importante no comportamento e desempenho. Resultados experimentais de um programa de monitoramento da argamassa desenvolvido pela equipe envolvida neste trabalho foi usado como referência. Para simular este processo de secagem, é utilizado um software implementado pelo Método das Diferenças Finitas (MDF). O software foi utilizado para identificar os principais parâmetros do material. A estratégia de modelagem (MC 2010) foi primeiramente aplicada aos resultados experimentais de corpos de prova cilíndricos, em sequência, aos resultados experimentais de um molde prismático. O modelo foi capaz de replicar os dados experimentais, de forma satisfatória. Destaca-se a relativa simplicidade da modelagem. Quando comparado com materiais como o concreto, foram encontrados maiores valores para D1 e fboundary. Para os corpos de prova estudados, os resultados experimentais e numéricos indicaram gradiente de umidade reduzido. Esses resultados estão associados à alta porosidade. Em sequência, considerando o par de valores obtidos na simulação numérica, estuda-se uma estrutura simulando uma construção real.

Resumo em Inglês:

ABSTRACT The structural safety of historical buildings often requires advanced structural analysis. Mortar typically exhibits complex composition and structural behavior. In different parts of the world, there is a significant number of historical constructions based on lime mortar. The moisture content in lime structures has a significant influence on their behavior and performance. Experimental results from a mortar monitoring program developed by the team involved in this study were used as a reference. To simulate this drying process, a software implemented in the Finite Difference Method is utilized (FDM). The software was employed to identify the key material parameters (D1 e fboundary), that best fit the experimental data, considering the approach presented by the Model Code 2010. The modeling strategy was initially applied to the experimental results of cylindrical specimens and subsequently to the experimental results of a prismatic mold. Overall, the model was able to fit satisfactorily. When compare the results with values for concrete, higher values were found for diffusivity and boundary coefficient. For the studied specimens, both experimental and numerical results indicated a reduced moisture gradient. These findings are associated with high porosity. Subsequently, considering the obtained parameter values, a structure simulating a real historic construction is analyzed. The results show that the humidity inside the inner parts remains elevated for long periods (~100 years).

Resumo em Inglês:

Abstract The coarse aggregate was replaced with iron slag by weight from 10 to 60% with 10% variations, and the self-compacting concrete samples were analyzed after 28 days of curing in water. This study assesses concrete sample flexural strength, splitting tensile strength, ultrasonic pulse velocity (UPV), acid resistance, surface water absorption, compressive strength, electrical resistance, and capillary water absorption. Additionally, the SEM (Scanning Electron Microscopy) analysis was performed to assess the microstructure level of the cement concrete mix. The samples with iron slag substituted at 20%, 40%, and 60% show greater compressive, flexural, and splitting tensile strengths (about 18.4%, 28.6%, and 16.9% higher) than the control samples. Moreover, adding coarse aggregate containing 10, 20, 30 and 40% of higher strength at compression was achieved with iron slag.

Resumo em Inglês:

Abstract Electrical contact material is the key to the work of isolation switch electrical system. The sterling silver coating often used cannot meet the current requirements of power transmission equipment because of contact heat caused by oxidation and wear, corrosion resistance and wear resistance. In this paper, graphene was added to silver brush plating bath to prepare graphene uniformly suspended silver-graphene composite plating bath, and silver-graphene composite coating was prepared on pure copper by brush plating technology. The optimum process parameters of silver-graphene composite coating were obtained by adjusting brush plating voltage and brush plating time. The results show that the self-corrosion potential of silver-graphene composite coating is slightly lower than that of pure silver coating, and the self-corrosion current is lower, indicating that the corrosion resistance of silver-graphene composite coating is better. Under different brush plating voltages, the coating shows the most positive corrosion potential and the lowest self-corrosion current density at 3V, and the corrosion resistance is the best at 2min under different brush plating time. When the graphene content is 30g/L, the binding rate between graphene and silver coating is the highest, the thickness of the coating is 23.5μm.

Resumo em Inglês:

Abstract Aim: This study aims to provide information about the mechanical characteristics of the files by comparing the torsional, bending and torsion strengths of glide path files with different properties. Method: WaveOne Gold (WOG)(15/v), ROTATE (15/.04), TruNatomy (17/.02), and Scope (17/.03) glide path files were used in this study. Torsional, bending, and buckling strength tests were performed using standard test methods according to ISO 3630-1 specifications (n = 12 from each group for each test). One-way analysis of variance was used to compare normally distributed data, and multiple comparisons were examined with Tukey’s honestly significant difference (HSD) and Tamhane’s T2 tests. The significance level was p < 0.050. Results: No statistically significant difference was found between the torsional strengths. The highest angular deviation value occurred in TruNatomy, while Scope had the highest bending and buckling strengths. Conclusion: The glide path instruments tested had different behaviours on bending, buckling and torsional resistance. Production methods and design features affect the mechanical properties of glide path files. For clinical use, the glide path file should be selected on a case-by-case basis.

Resumo em Inglês:

ABSTRACT This paper reports a novel coating containing activated TiO2 for improving corrosion resistance of Cu. In this study, three types of coatings were compared: one made from GPTMS (3-Glycidopropyltrimethoxysilane) (GC1), and two hybrid sol-gel coatings derived from G1 (solution organic) and activated with titanium. The Class I (GC2) coatings contained crystallized TiO2 particles integrated into the matrix, while the Class II (GC3) coatings used the liquid precursor TTIP (titanium (IV) isopropoxide). The three coatings, with thicknesses of 0.777 ± 0.5 μm (GC1), 2.054 ± 0.5 μm (GC2), and 3.774 ± 0.23 μm (GC3), were analyzed using XRD, optical profilometry, and SEM techniques. GC1 and GC3 exhibited uniform structures, while GC2 showed cracks due to TiO2 particles. After salt spray exposure per ASTM B117, the coatings were labeled GCE1, GCE2, and GCE3 for evaluation. Salt spray exposure caused SiO2 precipitates, impacting coating performance. GC3, with TTIP, showed a uniform surface and controlled roughness, leading to superior corrosion resistance (95% efficiency, 2764 Ω), outperforming GC2 (94% efficiency, 1331 Ω) and the substrate (918 Ω). TTIP improved adhesion and barrier formation, while TiO2 coatings (GC1, GC2) had increased roughness due to particle irregularities. GC3’s thicker, well-integrated structure contributed to its enhanced performance in corrosive environments.

Resumo em Inglês:

ABSTRACT The study investigates the mechanical and energy absorption characteristics of eco-friendly sandwich composites, using cork cores and natural fiber skins, to evaluate their feasibility as substitutes for conventional fiberglass composites in kayak manufacturing. The objective is to explore sustainable alternatives without compromising mechanical performance. Six composite plates with varying fiber densities and epoxy resins were manufactured and tested using ASTM standards for three-point bending and Charpy impact resistance. The bending tests revealed that plates with higher fiber densities exhibited greater mechanical strength, reaching up to 65 N in bending loads, while impact tests demonstrated varying energy absorption capabilities, with some plates absorbing up to 30 kJ/m2. Notably, laminates with bio-based epoxy resin performed similarly to those with synthetic resin in bending strength but showed slight differences in impact resistance. The study concludes that cork and natural fibers are viable substitutes for synthetic materials in kayaks, especially where environmental sustainability is prioritized. Plates with flax fiber skins and cork cores showed competitive mechanical properties, offering a potential sustainable solution for high-performance sporting goods, such as kayaks. Further optimization of these composites could accelerate their adoption in the sporting goods industry.

Resumo em Inglês:

Abstract This study aimed to enhance the mechanical properties of sandwich composites through structural modifications using E-glass fiber and polyurethane foam. Six types of sandwich composites were fabricated via the hand layup method, categorized based on core modifications focused on reinforcing the core to improve structural capabilities. Mechanical testing—including tensile, compression, flexural, impact, and hardness tests—revealed significant enhancements in strength and stiffness, particularly in composites with reinforced cores. Tensile tests showed that PCR20 exhibited the highest strength (1.59 MPa) and modulus (60.45 MPa), while compression tests indicated PCR20 had the highest strength (3.7819 MPa). Flexural tests revealed similar trends, with PCR20 showing the highest strength (10.17 MPa). Impact tests demonstrated that PCR10 was the strongest (243 J), and hardness tests showed PCR10 had the highest Shore D hardness (61). Scanning Electron Microscopy provided insights into the microstructural behavior and failure mechanisms, highlighting the ductile nature of reinforced composite columns. These findings underscore the effectiveness of core modifications in enhancing the mechanical performance of sandwich composites, emphasizing their potential across diverse industrial applications.This research can be applied in aerospace for lightweight yet strong structural components, in the automotive industry for reducing vehicle weight while maintaining durability, and in marine applications to enhance strength and corrosion resistance in shipbuilding.

Resumo em Inglês:

ABSTRACT This study introduces N-MBER, a novel soil stabilizer incorporating nano-SiO2, which significantly enhances the strength of cement-based soil mixtures. Experimental results show that N-MBER exhibits an exponential increase in strength over time, with strength improvements ranging from 15% to 50% compared to conventional stabilizers, depending on the nano-SiO2 content. The primary mechanism driving this enhancement is the increased formation of calcium silicate hydrate (C-S-H) gel, which contributes to improved durability and load-bearing capacity. Additionally, the nano-SiO2 improves particle structure, leading to greater overall stability. These advancements suggest that N-MBER not only improves soil stabilization but also has potential for reducing waste by minimizing reliance on traditional cement-based stabilizers. This development offers valuable insights into soil treatment techniques and presents a sustainable solution for infrastructure projects where soil strength is critical.

Resumo em Inglês:

ABSTRACT Pure magnesium (Mg) is a promising biodegradable biomaterial due to its excellent biocompatibility and appropriate elastic modulus. However, its high corrosion rate and insufficient mechanical properties limit its broader application. In this study, pure Mg is processed using high-pressure torsion (HPT) for 1, 2, and 5 turns. The evolution of the microstructure during the HPT process, as well as the microhardness distribution and corrosion resistance of the material after HPT, are investigated. The results reveal that HPT significantly refines the grain size of pure Mg, reducing it from about 5 mm to about 1 μm. This grain refinement increased the microhardness of pure Mg by 35%, and the microhardness values were uniformly distributed after 5 turns. The corrosion resistance of pure Mg improves with increasing number of HPT turns. This is indicated by a positive shift in the corrosion potential and a reduction in the rate of hydrogen evolution. The refined grain contributes to the formation of a denser and more uniform corrosion product layer, which enhances the protection of pure Mg substrates.

Resumo em Inglês:

ABSTRACT This investigation focused on the application of microwave pyrolysis technology, utilizing metal oxide clay minerals as both catalysts and microwave absorbers, with the goal of enhancing resource utilization efficiency in the treatment of oily sludge. Experimental results demonstrated that incorporating metal oxide clay minerals into the microwave pyrolysis process at 2000 W power substantially improved the yield of pyrolysis oil and gas, while simultaneously optimizing the products’ chemical composition. This study elucidates, for the first time, the distinct catalytic roles of three metal oxide clay minerals—hematite (Fe2O3), apatite (P2O5), and corundum (Al2O3)—in the microwave pyrolysis process. The findings indicate that these catalysts effectively increase the proportion of light fractions in pyrolysis oil and significantly reduce the production of harmful gases.The composition of combustible gases (H2 + CH4 + CO) in the pyrolysis gases exhibited increases of 7.224 wt%, 2.831 wt%, and 18.895 wt% for hematite, apatite, and corundum, respectively, relative to the control group. Specifically, hematite markedly enhanced the gas yield, particularly the concentrations of H2 and CO, and improved the quality of the pyrolysis oil, thereby augmenting the sludge’s energy recovery value. Furthermore, apatite exhibited outstanding nitrogen removal efficacy during the pyrolysis process, contributing to a reduction in nitrogen content in the pyrolysis oil and consequently diminishing the associated environmental risks.

Resumo em Inglês:

ABSTRACT In the automotive industry, the passive crash safety system of a vehicle plays an important role in occupant injury levels during frontal impact collisions. There are numerous strategies to safeguard the driver and passengers against a car collision around the globe. The crush box structure is a crucial energy absorber during frontal impacts. By absorbing the kinetic energy from a frontal accident, it protects the occupants. The numerical validation of crush boxes has been performed using the finite element code LS-DYNA with specific criteria and verified with an axial crush physical test. To perform mass optimization and determine the maximum energy absorption of the crush box, it is subjected to an axial crush test. The baseline design of the crush box has a thickness of 1.8 mm and uses steel DP650 material. The research focuses on improving the crush box’s performance in the axial crush test compared to the baseline version. To accomplish this, Steel DP450, Steel HD340LA, Steel DP650, and Aluminum Alloy AA_611, AA_6082, and AA_6056 material grades, along with two different designs and thicknesses in the range of 0.8 mm, 1 mm, 1.5 mm, 2 mm, and 2.5 mm, have been considered. The design of experiments has been conducted using FEA numerical nonlinear LS-DYNA code to find the optimal crush box design. Additionally, to validate the FEA simulation results, a physical axial crush test was performed on the crush boxes. The physical tests correlated with the FEA results by 85.6%. As a result, performance improvement was achieved with design-2, using aluminum alloy AA_6056 and a 2.5 mm thickness combination compared to the baseline. The deformation energy absorption increased by 36.76%, and mass optimization was achieved by 38.28%. The 36.76% increase in deformation energy absorption of crush box signifies a substantial improvement in protecting occupants during frontal impacts. This can translate to fewer severe injuries in real-world collisions. Achieving a 38.28% mass reduction without compromising safety is critical for improving vehicle efficiency. Lighter vehicles consume less fuel, have lower emissions, and extend the driving range of electric vehicles, directly contributing to environmental sustainability.

Resumo em Inglês:

ABSTRACT Nanocomposites are the combination of fibers, resin and nanofillers, and it is indeed the promising materials for many industrial applications. In the present study, the reinforcement Anogeissus latifolia (AL) gum powder of 40% is mixed with polyester (P) of 60% to produce unique hybrid polyester (ALP) resin matrix, the same is feeded with three different volume fractions of 1%, 3% and 5% Fly Ash Nano Powder (FANP) as a binding agent. These compositions applied on Abaca (AB), hemp (HE) and kenaf (KE) mats to produce the individual three layers composite fibers. The findings of dynamic mechanical analysis (DMA) shows that natural fiber materials with three different volume fractions (1%, 2% and 3%) mixing in each composition impregnated ALP resin have improved the stiffness compared to hybrid ALP resin. Damping factor (Tan δ) is observed to be least in AB/HE/KE mats for three different volume fractions nano powder feeding in each composition impregnated ALP resin as compared to hybrid ALP resin. The tensile strength, hardness and impact strength of raw AB fiber mats with 3% nano powder mixing in HR composites has reached the maximum value of 49.2 MPa, 17.4 BHN and 0.83 J. The improvements were 25%, 19% and 28% for the tensile, hardness and impact strengths, respectively.

Resumo em Inglês:

ABSTRACT Textile pilling is a persistent issue that results in an unattractive surface on garments, impacting their aesthetic and commercial value. This study employs image processing and machine learning techniques to grade fleece textiles based on pilling evaluation. Two approaches were explored: the first utilized a discrete Fourier transform combined with Gaussian filtering, while the second employed Daubechies wavelets. Binarization was used to isolate textile pilling from the surrounding fabric area. In this study, morphological and topological image processing techniques were applied to extract key features from the image data, creating a comprehensive database for fabric analysis. Machine learning techniques, specifically Support Vector Machine (SVM) and Artificial Neural Networks (ANN), were then used to objectively address the textile grading problem. The Fourier-Gaussian approach achieved classification accuracies of 95.67% with ANN and 92.34% with SVM, while the Daubechies wavelet approach yielded accuracies of 94.23% and 90.67%, respectively. In terms of pilling detection, the Fourier-Gaussian method identified 67 instances of pilling with a pilling area of 1674 units, whereas the Daubechies wavelets method detected 56 instances with a pilling area of 654 units. This automated system enhances textile quality assessment and production efficiency by effectively detecting and quantifying pilling.

Resumo em Inglês:

Abstract Phosphogypsum (PG) is an industrial by-product and it has the binding properties to produce non-fired tile. Sisal fibers were supplemented with phosphogypsum to enrich the strength of the tile. In this study, the eco-friendliness of utilizing phosphogypsum with Sisal fiber in non-fired has been assessed to find the environmental impact of PG tile and compared with conventional tile. The physiochemical properties of phosphogypsum and Sisal fiber were analyzed. The strength characteristics of the phosphogypsum and Sisal combined tile have been test verified by pressing hydration process. The ideal water content and fiber content for different pressing pressures have been determined from the experimental investigation. Phosphogypsum tiles consisting of 6 wt.% sisal fiber exhibited maximum bending stress of 16.5 MPa under 15 MPa loading. Production of non-fired tile largely reduces the energy consumption and environmental impacts over conventional tile production.

Resumo em Inglês:

ABSTRACT A mathematical model based on surface roughness and material rate reduction response variables was used to evaluate and predict die sinking electrical discharge machining (EDM) parameters like peak current and pulse active and inactive states. In this study, we examined our model’s ANOVA using p and f tests on Inconel 800 to enhance process characteristics based on their response to the surface method. The ANOVA results show that the maximum current value dominates MRR, followed by pulse active state and pulse inactive state. We use the Composite Desirability (CD) function to obtain the most favourable characteristics. During optimisation, the goal is to set upper and lower limits for MRR and surface roughness, respectively. The determination of the most favourable configuration for process variables is 15 kA, 17 μs, and 24 μs for maximum current, pulse active state, and pulse inactive state, respectively. At optimal parameters of highest MRR of 0.1423 mm3/min and lowest value for surface roughness is 1.8946 μm were predicted. Confirmation experiments show that the anticipated values are very closely matched with the findings from experiments with less than 5% error.

Resumo em Português:

RESUMO A carboximetilcelulose de sódio (CMC) é um sal celulósico obtido por meio da alcalinização da celulose e posterior eterificação do álcali celulósico com excesso de solvente orgânico. A CMC é utilizada como agente espessante, umectante, aglutinante, entre outros. Comumente ela é sintetizada a partir da celulose vegetal ou também a partir de celulose bacteriana (CB). O objetivo deste estudo foi sintetizar a CMC utilizando CB produzida pelo scoby de kombucha, para valorizar esse resíduo, utilizando 3 diferentes solventes orgânicos, isopropanol, butan-1-ol e pentan-1-ol. Após a síntese, as CMCs foram caraterizadas por rendimento, teor de umidade, grau de substituição (GS), pH, viscosidade, espectroscopia no infravermelho com transformada de Fourier (FTIR), difratometria de raios-x (DRX), termogravimetria e termogravimetria derivada (TG/DTG). Os resultados comprovaram a síntese das CMCs e apresentaram diminuição da temperatura de degradação e da cristalinidade em comparação à CB pura. Por fim, a CMC produzida com isopropanol obteve melhores resultados em comparação à literatura, apresentado maior rendimento (197,62%), maior grau de substituição (0,26 ± 0,05), maior viscosidade (11,33 ± 0,48 cP) e menor cristalinidade (32,45%). No entanto, é necessário um estudo utilizando um número maior de amostras para que se obtenha resultados mais precisos acerca do melhor solvente.

Resumo em Inglês:

ABSTRACT Sodium carboxymethyl cellulose (CMC) is a cellulosic salt obtained by the cellulose alkalinization and later etherification of the cellulosic alkali with excess organic solvent. CMC is used as a thickening agent, humectant, binder, and others. It is usually synthesized from vegetable cellulose or also by bacterial cellulose (BC). The objective of this study is to synthesize CMC using bacterial cellulose produced by kombucha scoby to value this residue, using 3 different organic solvents, isopropanol, butan-1-ol and pentan-1-ol. After the synthesis, the CMCs were characterized by yield, moisture content, substitution degree (DS), pH, viscosity, Fourier Transform Infrared spectroscopy (FTIR), x-ray diffractometry (XRD), and thermogravimetry and derivative thermogravimetry (TG/DTG). The results proved the CMC synthesis and presented a decrease of the degradation temperature, and crystallinity in comparison to pure BC. Finally, the CMC produced with isopropanol had the best results compared to the literature, presenting higher yield (197,62%), higher substitution degree (0,26 ± 0,05), higher viscosity (11,33 ± 0,48 cP) e minor crystallinity (32,45%). However, a study with more samples would be necessary to obtain more precise results about the better solvent.

Resumo em Inglês:

ABSTRACT This study investigates the effect of alumina (Al2O3) nanoparticles on the performance of geopolymer concrete composed of fly ash and ground granulated blast furnace slag (GGBS). The research focuses on the influence of nano-alumina on workability, mechanical strength, and durability. Results show that incorporating 2% nano-alumina, by mass of fly ash, yields optimal improvements in compaction, split tensile strength, and flexural strength. Additionally, the concrete exhibited enhanced resistance to water absorption, acidic environments, and salt solutions with nano-alumina content up to 2%. However, exceeding this percentage led to a decline in mechanical properties. These findings indicate that 2% nano-alumina is the ideal concentration for maximizing both the mechanical performance and durability of geopolymer concrete. The study underscores the potential of nano-engineered geopolymer concrete as a promising alternative to conventional concrete in the construction industry.

Resumo em Inglês:

ABSTRACT This research focuses on optimizing the hydrolysis process for acid-soluble titanium slag in TiO2 production to enhance product quality. Several parameters were investigated including free acid concentration, temperature and initial equivalent TiO2 concentration. Response surface methodology was employed to determine the optimal conditions: 4.2 M acid concentration, 95 g/L initial TiO2 concentration, and 112 °C, yielding a hydrolysis efficiency of 97.1 ± 0.3%. The optimized process produced TiO2 with 99.33 wt% purity, uniform particle size (D50 = 15.2 μm), and spherical morphology. Kinetic studies revealed pseudo-second-order reaction kinetics with an activation energy of 58.6 kJ/mol. The TiO2 exhibited photocatalytic activity of 85.2% dye degradation after 60 min, surpassing a commercial pigment-grade TiO2. Economic analysis indicated a production cost of $1,850 per ton, an NPV of $28.5 million, and an IRR of 25.6% for a 10,000 ton/year plant. The optimized process offers a sustainable and cost-effective approach for high-quality TiO2 production from titanium slag.

Resumo em Inglês:

ABSTRACT The greatest accomplishment in concrete technology to date has been the development of admixtures, which modify the properties of the concrete according to requirements. Admixtures that can be produced synthetically from natural sources to mimic the qualities of commercially available admixtures are known as "bio admixtures." Bio admixtures are made from microbes and plants, and their interactions with concrete are investigated. Cassava starch and xanthan gum combined yield a high-performing bio additive with enhanced adhesiveness. Along with the concrete, different combinations of bio additive are added in weight percentages of 0.5 wt%, 1 wt%, and 1.5 wt%. The paper examines the fresh concrete properties, the workability of concrete that has been added bio admixture, and the behavior of bio admixture concrete against flexural load, tensile loading, and compression pressures. By comparing the results with those of the control mix of M25 mix proportion of the concrete, the best mix combination of the bio additive combined with the concrete is determined. When 1.5 weight percent of bio additive is added to the concrete matrix, both in the fresh and hardened concrete states, performance is improved.

Resumo em Inglês:

ABSTRACT This research explores the synergistic effects of natural fiber reinforcement, specifically manila hemp, and silica fume incorporation on the performance of high-strength concrete (HSC). Various concrete mixtures were developed with different proportions of natural fibers (0%, 0.5%, 1.0%, 1.5%, and 2.0% by volume) and silica fume (0% to 30% by increment of 5% in weight of cement). A series of tests were conducted to evaluate workability, mechanical properties (including compressive, tensile, and flexural strength), and flexural aspects (such as deflection of beam). The findings demonstrate that incorporating up to 1.5% natural fibers and silica fume content up to 20% was found to improve mechanical property of 21% and flexural property of 18% due to its pozzolanic properties and ability to optimize particle packing. However, increasing the fiber and silica fume content beyond these levels resulted in reduced workability and only minimal improvements in strength. The study identified an optimal mixture consisting of 1.0% natural fibers and 20% silica fume, achieving a balance between improved mechanical properties, enhanced flexural behavior, and acceptable workability. This combined approach provides a promising strategy for developing high-strength concrete with advanced performance.

Resumo em Inglês:

ABSTRACT In todayʼs competitive construction industry, selecting the right suppliers for materials like M-Sand is crucial as it significantly affects both qualitative and quantitative outcomes. This paper examines the selection of the best M-Sand suppliers using Multi-Criteria Decision-Making (MCDM) methods. Initially, 13 qualitative criteria were identified by an expert panel, and the Fuzzy Delphi Method was employed to narrow these down to the five most important criteria. These criteria are essential for construction companies to make informed supplier choices. To determine the weight of each criterion, the study applied the Analytical Hierarchy Process (AHP) and fuzzy AHP, while the ranking of alternative suppliers was performed using the Fuzzy TOPSIS model. Recognizing AHP's potential inconsistency in evaluating qualitative criteria, the DEA model was integrated to balance qualitative and quantitative factors. The research aims to guide construction companies in selecting environmentally sustainable suppliers. Additionally, it explores the integration of alternative fine aggregates like Manufactured Sand (MS). The Consistency Index (CI) was calculated as 0.065. According to the closeness coefficient (C*), Alternative A3 is ranked first with a value of 0.155, followed by A4 (0.151), A2 (0.144), and A1 (0.141).

Resumo em Inglês:

ABSTRACT Nanotechnology is being investigated as a potential solution to enhance the strength and durability of high-strength concrete (HSC). The aim of this paper is to provide high-strength concrete, silica fume has used to provide matrix densification of concrete with high silica content and pozzolanic reactivity, and metakaolin which is well known for its high purity and fine particle sizes. Totally 13 mixes were prepared one with control mix and 12 mixes with the variation of metakaolin and silica upto 20% replacement individually with the increment of 5% from 5% to 20% in OPC. The results show that silica fume and metakaolin used in combination has been significantly effective not only in increasing the engineering properties of HSCs but also in significantly increasing the resistance to environmental damage. The findings suggest that using these nanomaterials includes in concrete mixes, which can lead to more flexible industries underlining the potential that could revolutionize concrete by providing a way to manufacturing better building materials that last longer and reduce maintenance costs.

Resumo em Português:

RESUMO A maioria dos estudos realizados no Brasil sobre o comportamento de conexões em estruturas de madeira é de natureza experimental, com poucos utilizando análises numéricas baseadas no Método dos Elementos Finitos (FEM). Em testes de embutimento, além de determinar os valores experimentais de resistência, é crucial entender os pontos de concentração de estresse para identificar os principais modos de falha. Este estudo teve como objetivo apresentar uma estratégia de modelagem numérica para monitorar o comportamento dos espécimes em testes de embutimento de acordo com a norma BS EN 383: 2007 [1]. Para a simulação numérica, utilizou-se o software ANSYS [2], considerando vários critérios de resistência para os materiais envolvidos. Os modelos incorporaram propriedades elásticas e plásticas dos materiais, obtidas por caracterização experimental em laboratório. Foram realizados testes experimentais de embutimento em espécimes nas direções paralela e perpendicular às fibras, usando pinos metálicos de 6.72 mm de diâmetro para calibração dos resultados numéricos. A estratégia de modelagem numérica proposta permitiu a análise global dos espécimes de teste de embutimento, bem como a investigação de aspectos localizados de interesse, como concentrações de estresse, um fator difícil de quantificar em análises experimentais.

Resumo em Inglês:

ABSTRACT Most studies conducted in Brazil to analyze the behavior of connections for wooden structures have an experimental nature, and few studies consider numerical analyses based on the Finite Element Method (FEM). In embedment tests, understanding stress concentration points is crucial for identifying primary failure modes and determining the experimental strength values. The objective of this study was to present a numerical modeling strategy to monitor the behavior of test specimens in embedment tests according to BS EN 383: 2007 [1]. The ANSYS [2] software was employed for numerical modeling, considering various strength criteria for the involved materials. The models incorporated elastic and plastic properties of the materials obtained through laboratory experimental characterization. Experimental embedment tests were conducted on specimens in parallel and perpendicular directions to the fibers, using 6.72 mm diameter metal pins for numerical result calibration. The proposed numerical modeling strategy allowed for the global analysis of embedment test specimens and the examination of localized aspects of interest, such as stress concentrations, a factor challenging to quantify in experimental analyses.

Resumo em Inglês:

ABSTRACT Magneto Rheological Elastomers (MRE) are composite intelligent materials, which can substantially change their viscoelastic properties due to their high magneto-sensitivity in response to different regimes of external magnetic field. The practical application of MR materials demonstrates great potential for several areas, as indicates the increasing number of patents registered in the last decade. For the dynamic characterization of the material, an original experimental arrangement was developed, from the creation of customized algorithms to the physical assembly of equipment, with the setup consisting of basic equipment used in vibration studies. Tests were carried out with a maximum strain of below 2.5%, the sampling frequency varied between 10 – 60 Hz under a single manually controlled input stress, with average between cycles of 1.66 kPa, and 2.19% deviation. The results showed expected behaviour and coherence with similar research, showing a gain in viscoelastic properties of 239% for shear modulus and 466% for viscosity in the maximum field of 500 mT. The Kelvin-Voigt model was used to numerically obtain the material properties, the error linked to the model (adaptation) was quantified at each acquisition cycle, with an average value of 6.33%, considered satisfactory by the work group, since the application in structures requires safety coefficients with higher values. The results obtained deepen the understanding of the material’s behaviour, exploring specific input values, and also demonstrate the viability of the experimental setup and the application of MREs for the development of vibration control devices.

Resumo em Inglês:

ABSTRACT The unique type of concrete that is most frequently employed is fiber reinforced concrete. Typically, only one fiber is utilized in fiber-reinforced concrete. This research primarily focuses upon the influence of fiber on its addition to concrete. In this study, bending behavior of fiber-reinforced concrete beams under cyclic pressure is investigated using hybridized polypropylene and steel fibers. There have been six different mixtures created, one of which being regular concrete. Monofilaments have been prepared from equal composition of steel and polypropylene with 0.5%. Apart from that hybridized combinations were also prepared using 0.12% steel fiber and 0.38% polypropylene fiber, 0.12% steel fiber and 0.38% polypropylene fiber, and 0.12% steel fiber and 0.38% polypropylene fiber. Superior flexural properties were observed with hybridized mix combinations ensured through experimental and numerical studies.

Resumo em Inglês:

ABSTRACT The primary goal of this study is to enhance surface defect detection in steel manufacturing through advanced machine learning techniques. Traditional inspection methods often fall short in terms of accuracy and efficiency, necessitating more robust solutions. This paper presents DBCW-YOLO, an optimized version of the YOLOv5 framework, designed to improve defect detection by integrating attention mechanisms and enhanced feature extraction techniques. The model incorporates the BiFPN technique to maximize feature map fusion across multiple scales, and CARAFE upsampling expands the network’s receptive area, effectively utilizing neighboring data for better detection. Additionally, WIoU introduces a dynamic, non-monotonic focusing mechanism in the loss function, addressing the issue of accuracy degradation caused by sample inhomogeneity. The model's performance was evaluated on multiple defect categories: crazing (Cr), inclusions (In), patches (Pa), pits and scales (PS), roll scale (RS), and scratches (Sc). DBCW-YOLO demonstrated significant improvements in Average Precision (AP) compared to the baseline YOLOv5m model, with AP for Cr increasing from 35.69% to 70.25%, In from 60.25% to 76.85%, and PS from 59.74% to 92.36%. These results confirm that DBCW-YOLO is a highly effective and efficient tool for automating surface defect detection in the steel industry, significantly outperforming the baseline model.

Resumo em Inglês:

ABSTRACT The flexibility of Aluminium Metal Matrix Composite (AMMC) is enormous in all aspect of manufacturing and electrochemical micro machining (ECMM) is an increasingly prevalent method due to its no tool wear, high precision, burr-free machining surface and non-invasive machining surface for all kind of materials. Hence, this present work investigated the ECMM process with biocompatible polymer dissolution mediums for electrolyte and their results are compared with regular aqueous medium. The bio conjugate agents such as bio polymer hydrogel and ethylene glycol is employed as solid bio polymer electrolyte (SBPE) and ethylene glycol electrolyte (EGLE) respectively to machine micro-holes on the AMMC work material. The results are compared with regular aqueous sodium nitrate electrolyte (ASNE). The machining performances are estimated by means of material removal rate (MRR) and overcut (OC). The results predicted that MRR increases for SBPE and EGLE by 2.47 times and 2.09 times respectively for the parametric mixture of 9V, 31 g/l and 65% than ASNE. The analysis taken with the field emission scanning electron microscope (FESEM) to determine the effect of SBPE and EGLE on the surface topography and interior machined edges of a micro-hole.

Resumo em Inglês:

ABSTRACT Quenching is a process that generates different properties in materials depending on its conditions and mediums. Initially, during the quenching process, electrolyte molecules are adsorpted on the metal surface, resulting in the formation of a vapor layer, in addition to bubbles and microexplosions, which vary according to the size of the electrolyte molecule. This affects the microstructure obtained, as well as the resulting mechanical properties. However, depending on the application of the material, the samples, after being quenched, require corrosion resistance treatments. Among these processes is phosphating, which is frequently applied to metal surfaces, especially for the anchoring of paints, due to the formation of iron phosphate. Therefore, seeking to achieve increased corrosion resistance in quenching processes, the main objective of this study is to verify whether phosphorus can be incorporated into AISI 4340 steel during quenching and whether the resulting layer improves anticorrosive performance. To this end, AISI 4340 samples were annealed and quenched in H2O and 2% H3PO4. The samples were analyzed as to their quenching process (via video analysis), microstructure, microhardness, morphology, EDS (energy-dispersive spectroscopy) and electrochemical measurement of potentiodynamic polarization. The samples tempered in 2% H3PO4 formed scale possibly containing Fe2O3 and FePO4. However, the scale showed slabbing, which compromises the corrosion resistance of these samples compared to the water-quenched samples. Nevertheless, the results showed for the first time that phosphorus can be incorporated into the surface layer of the scale created during the quenching of AISI 4340 in 2% H3PO4.

Resumo em Inglês:

ABSTRACT In this study work, the impact of metasteatite on the mechanical and microstructural properties of magnesium oxychloride cement (MOC) is investigated. The MOC paste cubes with metasteatite concentrations ranging from 0% to 25% with 5% interval was tested to compressive strength at curing ages of 3, 14, and 28 days. The microstructural properties of MOC matrix with varying content of metasteatite replacement were analyzed utilizing scanning electron microscopy (SEM) images through image processing technique. Further, it is quantified with porosity values and pore size distributions. TGA was performed to elucidate the mechanism underlying the improved water resistance of the novel MOC. The results showed that incorporating metasteatite into the MOC matrix significantly reduced the compressive strength at all curing ages compared with the control sample. Each mixture exhibited a notable pattern of prolonged hydration time, with a substantial increase in strength at 14 and 28 days containing 10–25wt.% of metasteatite. The potential for strength retention in MOC specimens containing metasteatite of 10% was significantly enhanced compared with that of the control specimen. The addition of metasteatite enhanced the porosity and pore structure, and the best results were achieved with a replacement rate of 10% in the MOC matrix.

Resumo em Português:

RESUMOAs transformações microestruturais do aço AHSS do tipo DP 800 foram estudadas com o objetivo de se investigar a influência dos tratamentos térmicos na microestrutura e nas propriedades mecânicas deste aço modificado; versatilizando sua gama de aplicações. O material na condição de como recebido foi submetido a um ensaio de dilatometria, para identificação dos domínios de transformação de fases. Depois de identificados, foram produzidas no material como recebido, algumas sequências térmicas feitas com resfriamento rápido a partir da solubilização parcial (α + γ) a 840°C e total (γ) a, 860°C e 880°C, seguidos de resfriamento. Após os tratamentos, sem revenimento, o material foi submetido a metalografia tradicional e posterior caracterização microestrutural com microscopia de varredura. Depois da caracterização microestrutural os materiais como recebido e tratados nas diferentes temperaturas foram submetidos a ensaios de tração uniaxial. As microestruturas mostraram que o material como recebido é constituído por uma matriz ferrítica, com grão contornados por martensita e bainita. A microestrutura do material resfriado a partir de 840°C mostrou, como era de se esperar, austenita residual, a ferrita, pouca bainita e um aumento significativo no teor de martensita. O resfriamento a partir de 860°C e 880°C produziram resultados, semelhantes, porém sem austenita residual. As propriedades mecânicas revelaram que o aumento do teor de martensita aumenta significativamente o limite de resistência, mas com perda da ductilidade.

Resumo em Inglês:

ABSTRACTThe microstructural transformations of AHSS steel of type DP 800 were studied in order to investigate the influence of heat treatments on the microstructure and mechanical properties of this modified steel; versatilizing its range of applications. The as received material was submitted to a dilatometry test to identify the phase transformation domains. After identification, some thermal sequences were produced in the as received material, made with rapid cooling both in partial solubilization (α + γ) at 840°C and total solubilization (γ) at 860°C and 880°C, followed by cooling. After treatments, without tempering, the material was subjected to traditional metallography and subsequent microstructural characterization with scanning microscopy. After the microstructural characterization, the materials, as received and treated at different temperatures, were subjected to uniaxial tensile tests. The microstructures showed that the as received material is constituted by a ferritic matrix, with grain contoured by martensite and bainite. The microstructure of the cooled material from 840°C showed, as expected, residual austenite, ferrite, little bainite and a significant increase in martensite content. The microstructures showed that the as received material is constituted by a ferritic matrix, with grain contoured by martensite and bainite. The microstructure of the cooled material from 840°C showed, as expected, residual austenite, ferrite, little bainite and a significant increase in martensite content. Cooling from 860°C and 880°C produced similar results, but without residual austenite. The mechanical properties revealed that the increase in martensite content increases significantly the strength limit, but with loss of ductility.

Resumo em Inglês:

ABSTRACTThe current work utilized power tools such as artificial neural networks (ANNs) to predict the durability parameters of concrete where partial replacement for coarse aggregate crushed ceramic waste. The concrete mix were subjected to systematic evaluation of compressive strength, water absorption, chloride diffusivity, and capillary absorption, with ceramic waste replacement levels ranging from 0% to 100%. The results show that incorporating ceramic waste enhances the mechanical and durability properties up to a certain replacement level, improving compressive strength and reducing water and chloride ion penetration. On the other hand, higher replacement levels led to an increase in porosity and adversely affected long-term durability properties. In current work, ANNs with various architectures were trained and tested on the above parameters and show varying performance based on model complexity and data quality. The models with optimal complexity demonstrated strong predictive capabilities for compressive strength, water absorption, and chloride diffusivity. The current findings illustrate the potential of ANNs in optimizing concrete mix with the replacement of recycled materials, balancing performance, durability, and sustainability.

Resumo em Inglês:

ABSTRACTNanofluids have garnered significant attention in thermal management systems due to their superior heat transfer properties compared to conventional fluids. This study explores the thermal performance of heat pipes filled with silver nanoparticle-based nanofluids with varying surface modifications. Surface modifiers, including Polyvinylpyrrolidone (PVP), Polyethylene Glycol (PEG), Lipoic Acid, Branched Polyethylenimine (BPEI), and Citrate, were used to enhance nanoparticle stability and dispersion. The study aimed to evaluate the effect of these surface modifications on thermal resistance and overall heat transfer coefficient in heat pipes. Nanofluids containing a 0.2% weight concentration of surface-modified silver nanoparticles were prepared using ultrasonication. The heat pipes were tested with two filling ratios under heat inputs ranging from 40 W to 80 W. BPEI-coated nanoparticles exhibited the best performance, decreasing thermal resistance from 0.12 K/W at 40 W to 0.08 K/W at 80 W. The heat transfer coefficient for BPEI increased from 870 W/m2K to 910 W/m2K over the same range. Lipoic Acid-coated nanoparticles also showed good performance, reducing thermal resistance from 0.13 K/W to 0.09 K/W. Surface modification is crucial in enhancing nanofluid thermal properties, with BPEI-coated nanoparticles offering the best results. These findings support the use of surface-modified nanofluids in thermal management applications.

Resumo em Inglês:

ABSTRACTIn order to fulfil rising energy demands and reduce pollutants in the environment, renewables are more crucial. Setting up communications again in the areas impacted requires easy alternate sources of energy after natural catastrophes. The handheld Vertical Axis Windmill Turbine can be used. FDM technique is believed to constitute over 70% of all 3D printing methods worldwide, popularly known as additive manufacturing, which has been prevalent in recent years. FDM is a technology that is based on the fact that the thermoplastic materials in the fiber are suddenly molten and connecting with the preceding layer. In this work (FEA), the stress analysis of PLA materials generated through the FDM-3B technology was investigated using the Finite Element method. In the ANSYS-FEA program, the material characteristics are specified. By comparing isotropic material with FDM-3D printed components, the findings were addressed in the literature. One of the most popular and frequently used techniques for the production of plastic components is FDM (Fuse Deposition Modelling). The study conducted comparisons of the efficiency of the turbine vertical axis Windmill. Conclusions about the practicality and viability of 3D wind turbines are drawn, and opportunities for additional development are emphasized.

Resumo em Inglês:

ABSTRACTThe growing demand for gypsum in civil construction has stimulated studies to improve flexural strength and reduce its layer with water. Therefore, the objective was to evaluate the influence of incorporating multi-walled carbon nanotubes (MWCNT) into the gypsum matrix on its physical and mechanical properties. In the production of composites, the gypsum mass was obtained by different levels of functionalized MWCNT: 0%, 0.001%, 0.002%, 0.003% and 0.004%. Apparent density, observation of water and flexural strength and analysis of the nanocomposites were verified. Replacing gypsum with MWCNT can cause water absorption by 8.33% compared to the control. The apparent density of the compounds showed an increase, with the concentration of 0.004 MWCNT showing an increase of 3.21% when compared to the reference. Compounds with contents of 0.001 and 0.003% of MWCNT showed an improvement in flexural strength values, presenting of 6 MPa. There were improvements for the insertion of 0.001 MWCNT (9 MPa) compared to the control (7 MPa). Thus, the results indicate that replacing gypsum with MWCNT is a viable alternative to improving the mechanical and physical properties of gypsum, which can increasingly expand its use in civil construction.

Resumo em Português:

RESUMOO uso de resíduos agroindustriais na construção civil tem aumentado nas últimas décadas, com destaque para o uso de cinza de bagaço de cana-de-açúcar (CBC) na produção de concreto, substituindo parcialmente o aglomerante ou o agregado miúdo. Esta pesquisa investigou a viabilidade de substituição parcial do agregado miúdo por CBC (sem moagem) na substituição parcial do agregado miúdo em concretos destinados à produção de blocos de pavimentação intertravada, nos teores de 0%, 5%, 10%, 15% e 20% da areia por CBC. Os blocos foram moldados em fôrmas hexagonais e submetidos a ensaios de resistência à compressão e absorção de água. Os resultados dos traços com substituição foram comparado com o traço de referência (0% de CBC). Os resultados indicaram que os traços com 15 e 20% de CBC atingiram os níveis de resistência e absorção exigidos. O traço com 20% de CBC apresentou os melhores resultados de resistência quando comparados aos demais traços com substituição, sendo que sua resistência à compressão foi a mais próxima ao traço de referência. Do ponto de vista da resistência à compressão, essa proporção foi a mais adequada, entre as substituições realizadas para essa aplicação.

Resumo em Inglês:

ABSTRACTThe use of agro-industrial waste in civil construction has increased in recent decades, mainly sugarcane bagasse ash (SBA) in concrete production, partially replacing the binder or fine aggregate. This study assessed the feasibility of using unground SBA as a partial substitute for fine aggregate in concrete designed for interlocking paving blocks. The research investigated replacing 5%, 10%, 15%, and 20% of sand with SBA. The blocks were cast in hexagonal molds and subjected to compressive strength and water absorption tests. The results were compared with concrete produced without SBA (reference). The results indicated that mixtures with higher CBC incorporation rates (15% and 20%) met the required levels of strength and absorption, demonstrating the feasibility of using CBC as a partial replacement for sand in interlocking pavements. The mixture with 20% CBC showed the best strength results compared to the other replacement mixtures, with its compressive strength being the closest to the reference mixture. From the perspective of compressive strength, this proportion was the most suitable among the substitutions carried out for this application, offering a sustainable and efficient solution for reusing agro-industrial waste in civil construction.

Resumo em Português:

RESUMO Este estudo investiga a incorporação de partículas finas de bambu, geralmente descartadas, em matrizes cimentícias como bio-agregados para bioconcretos. Durante a trituração dos colmos de bambu, são geradas partículas de diversas granulometrias, com até 13% do volume composto por partículas finas. O objetivo é caracterizar fisicamente e mecanicamente bioconcretos com substituição parcial de bio-agregados miúdos por finos de bambu em teores de 0%, 5%, 10% e 13% do volume total de bio-agregados. A matriz cimentícia utilizada é composta por 45% de cimento Portland, 35% de cinza volante e 20% de cinza de casca de arroz, com relação água/materiais cimentícios de 0,3 e 2% de cloreto de cálcio. Foram realizados ensaios de espalhamento e teor de ar incorporado no estado fresco, e ensaios de umidade, absorção capilar, retração por secagem e compressão uniaxial no estado endurecido. Os resultados indicam que bioconcretos com maior teor de finos são mais compactos e menos porosos, com menor absorção capilar (até 46% menor) e maior resistência à compressão (até 15,3% maior aos 28 dias), apesar de maior retração. Conclui-se que a utilização de 13% de bio-agregados finos melhora o desempenho geral do material, viabilizando o aproveitamento integral dos bio-agregados gerados.

Resumo em Inglês:

ABSTRACT This study investigates the incorporation of fine bamboo particles, typically discarded, into cementitious matrices as bio-aggregates for bioconcretes. During the crushing process of bamboo culms, particles of various sizes are produced, with up to 13% of the volume consisting of fine particles. The aim is to characterize the physical and mechanical properties of bioconcretes with partial replacement of coarse bio-aggregates by fine bamboo particles at proportions of 0%, 5%, 10%, and 13% of the total bio-aggregate volume. The cementitious matrix used comprises 45% Portland cement, 35% fly ash, and 20% rice husk ash, with a water/cementitious material ratio of 0.3 and 2% calcium chloride. Fresh state tests included spread and incorporated air content, while hardened state tests encompassed moisture content, capillary absorption, drying shrinkage, and uniaxial compression tests. Results indicate that bioconcretes with higher fine particle content are more compact and less porous, exhibiting reduced capillary absorption (up to 46% lower) and increased compressive strength (up to 15.3% higher at 28 days), despite greater shrinkage. It is concluded that using 13% fine bio-aggregates enhances the overall performance of the material, making full utilization of generated bio-aggregates feasible.

Resumo em Inglês:

ABSTRACT This study investigates the influence of wave-absorbing materials on the heating efficiency of microwave treatment in the remediation of contaminated soil, with a focus on the Tiruppur taluk region. The area was selected due to the significant contamination of soil and water bodies, particularly the Noyyal River, resulting from the direct discharge of dyeing waste. The materials tested include Fe3O4, SiC, and activated carbon, subjected to heating at temperatures of 100°C, 300°C, and 600°C. Microscopic analyses were conducted at a scale of 5 μm to observe any changes in morphology. The results demonstrate that although activated carbon exhibits greater thermal stability compared to Fe3O4, its wave-absorbing properties have a limited effect on the heating rate. SiC’s wave-absorbing capacity also does not significantly influence the heating rate. Notably, when subjected to continuous heating at 40°C, Fe3O4 begins to oxidize into Fe2O3, resulting in a 9% transformation. In addition, machine learning techniques were employed to enhance the analysis of soil properties and the efficiency of microwave heating. The findings suggest that while Fe3O4 and activated carbon are promising materials for microwave remediation, further research is needed to optimize their performance, particularly in the context of large-scale environmental applications.

Resumo em Inglês:

ABSTRACT The growth of industry in recent years has led to a gradual increase in concerns about heavy metal poisoning in water and soil, which, if ignored, might seriously endanger human health. Although copper (Cu) is a naturally occurring element that is widely distributed, exposure to high concentrations can have harmful effects on the body due to bioaccumulation and toxicity. With the help of biochar, an adsorbent made from the Roystonea Regia plant, batch adsorption experiments were utilized in this study to remove copper from aqueous solutions. Bentonite clay modifies the adsorbent̕s surface to boost its reactivity, For Cu the percentage removal efficiency was 72.62%. The equilibrium isotherms were defined by analyzing the experimental data with the help of Thomson model and Yoon Nelson. To ascertain the elemental composition and surface modification of the produced biochars, the surface area was assessed using SEM, EDAX and FTIR techniques both before and after the adsorption. The results of the study demonstrated that surface-modified biochar produced by Roystonea Regia performed effectively as an adsorbent to eliminate Cu2+ ions from effluent.

Resumo em Inglês:

ABSTRACT A steel-plate-provided concrete shear wall with parallel circular concrete-filled steel tube columns (P-CFST-SCSW) was investigated for engineering applications and deformation performance, and this study combines the characteristics of a P-CFST-SCSW to propose material strain limit values for various performance states of this shear wall. Firstly, 378 finite element models are designed using accurate finite element models, which include the ratio of axial compression and the ratio of shear-to-span, steel tube distance, and steel tube thickness. Furthermore, performance points are extracted from all the models, and the effect of each parameter on the limits of the deformation index of the P-CFST-SCSW is investigated. Finally, the machine learning algorithm is used to build models for predicting the deformation of the P-CFST-SCSW and analyze the importance of the feature. The results show that the range of performance point 5 is between 1/25 and 1/12, reflecting the improvement of the P-CFST-SCSW̕s ductility. Performance points are best predicted by the gradient-boosting decision tree model, with an R-squared value exceeding 0.9 across the test set. The importance of steel tube thickness increases gradually with the performance points. The shear-to-span ratio increases and subsequently decreases, unlike the axial compression ratio.

Resumo em Português:

RESUMO Neste trabalho foram utilizados resíduos de Medium Density Fiberboard (MDF) e madeira como cargas de reforço em compósitos de estrutura sanduiche. O MDF foi utilizado em diferentes proporções em espumas rígidas de poliuretano (PU) bem como em diferentes granulometrias; as placas externas foram produzidas com um compósito de polietileno de baixa densidade (PEBD) e copolímero de etileno acetato de vinila (EVA) (80:20) reforçadas com pó de madeira Pinus elliottii (20%). As espumas foram avaliadas quanto a resistência à compressão, densidade e morfologia. Já os compósitos com estrutura sanduíche foram avaliados quanto a resistência à flexão e isolamento térmico. Observou-se aumento na densidade das espumas com aumento do teor de cargas e redução de até 0,05 MPa na resistência à compressão quando adicionado cargas de MDF. A inserção de cargas nas espumas de PU gera colapso das células, levando a maior contração da espuma durante o processo de expansão. Nas análises realizadas no compósito com estrutura sanduíche, observou-se uma variação na resistência a flexão, com resistências superiores à espuma de PU puro para os compósitos com o núcleo de PU10A e PU10B, e valores de resistência menores nas demais amostras com carga.

Resumo em Inglês:

ABSTRACT In this work, waste Medium Density Fiberboard (MDF) and wood were used as reinforcing fillers in sandwich composites. MDF powder was used in different proportions in rigid polyurethane (PU) foams as well as in different grain sizes; the outer boards were produced with a composite of low-density polyethylene (LDPE) and ethylene vinyl acetate copolymer (EVA) (80:20) reinforced with Pinus elliottii wood powder (20%). The foams were assessed for compressive strength, density and morphology. The composites with a sandwich structure were evaluated for flexural strength and thermal insulation. An increase in the density of the foams was observed with an increase in the content and a reduction of up to 0.05 MPa in compressive strength when MDF fillers were added. The insertion of fillers in PU foams causes the cells to collapse, leading to greater contraction of the foam during the expansion process. In the analyses carried out on the composite with a sandwich structure, a variation in flexural strength was observed, with higher strengths at pure PU foam compared to the composites with the PU10A and PU10B core, and lower strength values in the other loaded samples.

Resumo em Inglês:

ABSTRACT Cracks in structures are discontinuities that occur due to stress, material degradation, or design flaws, compromising structural integrity. Detecting and analyzing cracks is crucial for assessing safety and determining maintenance needs. Various methods like image processing, machine learning, and deep learning are employed for accurate crack identification and classification. Advanced algorithms enhance detection accuracy and efficiency, leading to improved structural maintenance strategies. Addressing cracks promptly ensures prolonged infrastructure lifespan and safety. The goal of this research is to completely change the field of concrete cracking analysis through the use of cutting-edge machine learning technologies. The main objective is to design and implement a crack analysis system that uses cutting-edge techniques such as Convolutional Neural Network (CNN), support vector machine (SVM), and the k-nearest-neighbor (KNN). By harnessing the power of machine learning, the project aims to achieve unprecedented accuracy in crack detection, enabling precise identification of crack characteristics including length, width, and depth. Through meticulous coding and collaboration utilizing platforms like Google Colab, the study seeks to establish a robust framework for effectively and efficiently classifying cracks in structures. This innovative approach holds promise for enhancing structural integrity assessment and facilitating timely maintenance interventions, thus contributing to safer and more resilient infrastructure.

Resumo em Português:

RESUMO A presente pesquisa analisou a influência do empacotamento granular no concreto de pós reativos, com substituição dos agregados graúdos por pós residuais. As composições propostas visam garantir preenchimento de vazios com grãos de variadas formas e tamanhos e conferir homogeneidade e trabalhabilidade à mistura. O método buscou analisar diferentes combinações na composição do arranjo de finos de forma que a otimização do mesmo contribua para melhorar nas características mecânicas e físicas do compósito. Para tanto, foi realizado o teste de empacotamento de partículas com o software Emma, já no estado fresco da mistura, verificou-se o espalhamento e no estado endurecido foram realizados os ensaios de resistência à compressão, densidade de massa e absorção de água. Verificou-se que o empacotamento dos grãos influencia nas propriedades das argamassas, sendo que o proporcionamento com o maior fator de empacotamento (q = 0,5), obteve melhor índice de consistência, menor absorção de água e maior resistência à compressão axial. Sendo assim, dentre os proporcionamentos analisados, conclui-se que o proporcionamento de maior fator (q = 0,50) é o mais adequado concreto de pós-reativos, obtendo melhores características mecânicas e redução de porosidade, sendo o método de empacotamento dos grãos importante ferramenta para escolha do proporcionamento mais adequado.

Resumo em Inglês:

This study analyzed the influence of granular packing on reactive powder concrete, with replacement of coarse aggregates by residual powders. The proposed compositions aim to ensure filling of voids with grains of various shapes and sizes and to provide homogeneity and workability to the mixture. The method sought to analyze different combinations in the composition of the arrangement of fines so that its optimization contributes to improving the mechanical and physical characteristics of the composite. For this purpose, the particle packing test was performed with the Emma software, in the fresh state of the mixture, the spreading was verified and in the hardened state the tests of compressive strength, mass density and water absorption were performed. It was verified that the packing of the grains influences the properties of the mortars, and the proportion with the highest packing factor (q = 0.5) obtained a better consistency index, lower water absorption and greater resistance to axial compression. Therefore, among the proportions analyzed, it is concluded that the proportion with the highest factor (q = 0.50) is the most suitable reactive powder concrete, obtaining better mechanical characteristics and reducing porosity, with the grain packing method being an important tool for choosing the most suitable proportion.

Resumo em Inglês:

ABSTRACT The FRP composite has recently emerged as a promising alternative material in the construction industry. The need for lightweight materials with excellent tensile strength and good corrosion resistance has increased focus on composites reinforced with natural or synthetic fibers. This study focuses on the experimental study of slab size 600 mm × 450 mm × 50 mm with GFRP bars to replace conventional steel bars. The study examined the short-term behaviour of slab specimens with glass fiber-reinforced polymer bars and conventional steel bars subjected to static and static cyclic loadings. A comparative study is also done. The results are presented, discussed and compared the deflection, load-carrying capacity, strain distribution, cracking moment and failure mode, etc. The study concluded that the slab reinforced with GFRP bars shows 3.6% higher load-carrying capacity and 34.6% higher deflection than the traditional steel bars under static loading condition. The static cyclic loading condition shows 5.5% higher load-carrying capacity and 33.6% higher deflection in the GFRP bar reinforced slab than the conventional steel bar slab. The results show that the slab with GFRP bars resists higher load than conventional steel bars.

Resumo em Português:

RESUMO O presente estudo desenvolveu uma nova metodologia de processamento termomecânico, que consiste na combinação de técnicas de deformação plástica severa e tratamento térmico de reversão martensítica. Com o propósito de refinar a microestrutura de um aço inoxidável AISI 201 LN e obter um material com propriedades avançadas. Para isso, o material foi solubilizado a 1050 °C por 1 hora. Em seguida o aço foi deformado via extrusão em canal angular (ECAP) a 300 °C por 3 passes utilizando a rota BC, com intuito de reduzir o tamanho de grão (TG) e ao mesmo tempo aumentar a dureza do material, sem que ocorra a transformação martensítica. Posteriormente, o mesmo foi submetido ao forjamento rotativo, com 35% de redução do diâmetro, com intenção induzir a transformação martensítica e consequentemente o aumento da dureza. Por fim, o material foi tratado termicamente para reversão da martensita, a 750 °C por 15 minutos. Os resultados evidenciaram que não ocorreu transformação de fases no material submetido ao processo de ECAP, entretanto ocorreu um aumento significativo na dureza (cerca de 80%) no terceiro passe e uma redução do tamanho de grão. O forjamento rotativo promoveu a transformação martensítica e por consequência elevou em cerca de 170% a dureza. Após o tratamento de reversão, foi observado, pelas imagens de EBSD (Electron Backscatter Diffraction – Difração de elétrons retroespalhados) redução e a maior homogeneização do tamanho de grão, além do aumento na dureza do material quando comparado à condição de como recebido. As curvas de tração evidenciaram o aumento significativo no limite de escoamento e na tensão de ruptura do material.

Resumo em Inglês:

The present study developed a new methodology for thermo-mechanical processing, combining severe plastic deformation techniques and martensitic reversion heat treatment. The aim was to refine the microstructure of an AISI 201 LN stainless steel and obtain a material with advanced properties. The material was annealed at 1050 °C for 1 hour to achieve this. Subsequently, the steel was deformed via Equal Channel Angular Pressing (ECAP) at 300 °C for three passes using the BC route to reduce the grain size (GS) and simultaneously increase the material's hardness without martensitic transformation occurring. Afterward, it underwent rotary forging, with a 35% reduction in diameter, aiming to induce martensitic transformation and increase hardness. Finally, the material underwent heat treatment to revert the martensite at 750 °C for 15 minutes. The results showed no phase transformation occurred in the material subjected to the ECAP process. However, there was a significant increase in hardness (about 80%) after the third pass and a reduction in grain size. Swaging (rotary forging) promoted martensitic transformation, resulting in a 170% increase in hardness. After the reversion treatment, Electron Backscatter Diffraction (EBSD) images showed a reduction and greater homogenization of grain size, as well as an increase in material hardness compared to the as-received condition. Tensile curves showed a significant increase in yield strength and ultimate tensile strength of the material.

Resumo em Inglês:

ABSTRACT The application of ANN in forecasting wear rates during the manufacturing of novel hybrid composites is crucial for advancing material science, particularly in industries where wear resistance is critical, such as aerospace, automotive, and manufacturing. This present study is an investigation to form a hybrid novel metal composite of Aluminium alloy ADC12/BS/TiB2. The nanoparticles of biosilica and titanium diboride of varying weight percentages were added to the ADC12 matrix alloy, and the hybrid composite was fabricated via a stir-casting. A pin-on-disc wear device was used to determine the hybrid composites' dry sliding wear studies over a range of weights, velocities, and distances. Using ANOVA, the effect of material type on wear rate is determined to be statistically significant. ANN employs the Levenberg-Marquardt, which is aimed to reduce MSE using a back-propagation strategy. ADC12/BS/TiB2 hybrid composites experimental wearrate has been predicted using ANN models, and it has been determined that these forecasts exhibit excellent agreement with intended values. The use reinforcements have been shown by experimental and ANN technologies to significantly lower wear rates and the results indicated that for the load of 20 N, velocity of 3 m/s, and distance of 2500 m, a minimum wear of 0.00596 mm3/m may be attained.

Resumo em Inglês:

ABSTRACT With the development of electroless nickel plating technology, in order to meet the needs of some properties of the coating, people add nanoparticles on the basis of the original process, so that the electroless coating combines the unique functions of nano-materials. The application of electroless composite plating process on the surface of magnesium alloy and the introduction of ultrasonic wave can significantly improve the properties of the coating. Compared with the traditional chemical process, the ultrasonic composite coating has better performance in uniformity, compactness and grain refinement, and the reaction is more intense and the deposition speed is faster. It is found that ultrasonic power and temperature have positive effects on the hardness, corrosion resistance and plating rate of the coating, and the appropriate increase of ultrasonic power is helpful to improve the performance. In this paper, the optimum bath ratio was obtained by biorthogonal test: lactic acid 20 ml/L, citric acid 25g/L, succinic acid 9 g/L sodium acetate 15 g/L, and the optimum process parameters: power 60 W, temperature 60°C, pH 6.2, nanometer concentration 10 g/L. Through the experimental analysis, it is concluded that the ultrasonic electroless composite plating is more uniform, compact and finer than the conventional electroless composite plating.

Resumo em Inglês:

ABSTRACT Biomedical information encompasses various documents, offering researchers and medical practitioners valuable insights into the latest developments, validating and developing novel hypotheses, performing experiments, and interpreting results. Resources such as web information, multimedia documents, clinical trials, and medical reports also provide immense data. The growing size of these textual sources makes managing and extracting data challenging. Over recent decades, several automatic approaches have been developed to address text file issues for knowledge discovery and information extraction. Automatic biomedical text summarization techniques have been extensively explored to help researchers and clinicians handle large volumes of data. This paper presents an Automated Biomedical Document Summarization using Dwarf Mongoose Optimization with Graph Attention Networks (ABDS-DMOGAN) technique. The ABDS-DMOGAN model preprocesses biomedical documents to prepare them for summarization. It uses the GAN model for summarizing content from various biomedical documents. To enhance the GAN model’s summarization results, the DMO algorithm is applied for hyperparameter tuning. Extensive simulations demonstrate the improved performance of the ABDS-DMOGAN model, with outcomes showing its significant superiority over other existing deep learning approaches.

Resumo em Inglês:

ABSTRACT This present study investigates the mechanical characterization of polymer hybrid fibre-reinforced concrete. The study includes linear regression analysis and comparisons using various empirical codes to predict polymer hybrid fibre-reinforced concrete’s compressive and split tensile strength. The strength properties of the polymer hybrid fibre-reinforced concrete were studied in 8 mix groups, comprising 56 mixes, at various age periods: 7 and 28 days. The polypropylene and glass fibres were added in the range of (0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, and 1.4%), and the polymer content ranged from (1%, 2%, 3%, 4%, and 5%), respectively. The polymer hybrid fibre reinforced concrete compressive and split tensile strength properties were enhanced by adding the polypropylene fibre, glass fibre and polymer content. The optimum mix was compared to the control mix in eight mix groups. The compressive strength increased at 28 days by 19.79%, 23.68%, 8.30%, 11.15%, 19.49%, 23.72%, 7.05%, and 6.41%. The split tensile strength improved at 28 days by 25.66%, 30.48%, 8.40%, 11.46%, 19.65%, 23.88%, 24.10% and 18.18%, respectively. Moreover, linear regression analysis was conducted to predict the strength properties of polymer hybrid fibre-reinforced concrete, such as compressive strength and split tensile strength. The relationship between compressive strength and split tensile strength was analysed using the linear regression method, and the R2 values were found to be 0.86. Additionally, the split tensile strength is predicted using existing empirical formulas, and the predicted split tensile strength is closely correlated with the experimental split tensile strength. The linear regression analysis and existing empirical formulas aided in predicting the strength properties of the polymer hybrid fibre-reinforced concrete.

Resumo em Inglês:

ABSTRACT Stone columns are recognized as a highly effective technique for enhancing the load-bearing capacity and reducing settlement in soft clay soils. Recently, encased stone columns have become increasingly important in improving the properties of soft soils. In a series of controlled laboratory tests on prototype models, both uniform and non-uniform stone columns were examined under various loading conditions, with and without the application of geogrid encasement. The material characteristics of the soil and the stone columns, as well as their geometry, were the main subjects of this experimental study. The results revealed that geosynthetic encasement significantly reduced bulging and settlement, especially in non-uniform stone column configurations. The study found that using a non-uniform stone column design could reduce the quantity of materials required while still enhancing the soil's bearing capacity. The findings showed a significant improvement in performance due to the encasement, with the best load-settlement behavior occurring in columns where the encasement height was optimized for the specific geometry. This research underscores that a non-uniform encased stone column section can achieve results comparable to those of a traditional stone column.

Resumo em Inglês:

ABSTRACT Accurate prediction of concrete compressive strength is essential for ensuring the durability and safety of concrete structures. This study utilizes the Deep Forest (GC Forest) model to predict compressive strength based on nine key factors: Granulated Blast Furnace Slag, Pulverized Fuel Ash, Mixing Water, High-Range Plasticity Reducer, Crushed Stone, Sand, Curing Time, Portland Cement, and Compressive Strength. The Deep Forest model's performance was compared with 12 other machine learning models, including Linear Regression, k-Nearest Neighbors, Decision Tree, Support Vector Machine, Neural Network, Random Forest, and Gradient Boosting Machines. Model evaluations were conducted using the coefficient of determination (R2) on a dataset of the listed parameters. The Deep Forest model achieved the highest predictive accuracy, with an R2 value of 9.55, outperforming all other models. This result demonstrates the model's robustness, owing to its ensemble-based architecture that enhances generalization. The study emphasizes the effectiveness of advanced machine learning models like Deep Forest in optimizing concrete compressive strength predictions, contributing to improved structural design and quality control.

Resumo em Inglês:

ABSTRACT Cork is becoming recognized as a sustainable and renewable material owing to its low density, superior acoustic and thermal insulation properties, energy absorption capabilities, and environmental friendliness. Sustainability has catalyzed innovation in kayak production and several other industries. This project sought to develop an environmentally sustainable "sandwich" composite material including a cork agglomerate core, natural fiber facings, and bio-based epoxy resin. This study investigated several material combinations and produced laminate plates with a cork core, flax fiber skins (100–500 g/m2), and bio-epoxy resin. The composite was meticulously produced using vacuum pressing to ensure its integrity and functionality. The laminate plates were then subjected to extensive testing for mechanical qualities. Bending tests demonstrated favorable force-displacement characteristics for composites. Impact testing at 2.9 m/s recorded energy absorption of up to 1.99 J. The evaluation of several specimen orientations enabled a comprehensive assessment of composite performance. In bending tests, 500 g/m2 flax fiber laminates achieved a maximum load of 65 N and a displacement of 5.5 mm, comparable to standard fiberglass composites which recorded 60 N and 4 mm. Impact tests demonstrated that the cork core effectively absorbs energy, making it appropriate for rigorous applications. Density correlations indicated that flax laminates with a mass of 500 g/m2 exhibited the highest strength.

Resumo em Inglês:

ABSTRACT This study examines the friction and wear behavior of hybrid composite materials, with a focus on understanding how premixed reinforcement influences wear rate and coefficient of friction (COF) under varying conditions of load, sliding speed, and distance. The results indicate that increasing load and sliding speed generally raise both the wear rate and COF, with wear rates ranging from 58 µm to 100 µm and COF from 0.37 to 0.52. Notably, Sample S4 (20N/1.5 m/s/600 m) showed the lowest wear rate of 58 µm, while Sample S6 (20N/3.5 m/s/1000 m) exhibited the highest wear rate at 100 µm. Sample S5 (20N/2.5 m/s/800m) stood out with a wear rate of 61 µm and the lowest COF of 0.37, suggesting that premixed reinforcement can significantly enhance wear resistance under specific conditions. Advanced scanning electron microscopy (SEM) was utilized to analyze wear mechanisms, offering critical insights into the surface degradation processes. The study’s comprehensive evaluation of hybrid composites, supported by comparative analysis with existing systems, underscores their potential for high-stress applications in industries like aerospace and automotive, where durability and material performance are crucial.

Resumo em Inglês:

ABSTRACT Due to simple structure and easy-to-integration, metallic single slit array structure has attracted considerable attention and been widely investigated in recent years. A multi-channel comb filter composed of Au slit and graphene was proposed in this paper. It works at infrared wavelength range with narrow single-channel bandwidth and high pass band transmittance. After structure optimization, the single-channel bandwidth of the comb filter can reach 4.2 nm, which is nearly one time higher than the existing multi-channel comb filter based on surface plasmon polariton. Additionally, the structure of the filter is simple and more suitable for on-chip integration.

Resumo em Inglês:

ABSTRACT This paper attempts to compare the Experimental results such as Ultimate Load, Maximum Bending moment and flexural strength of PVC (Polyvinyl chloride) Rubber Composite RCC beams as both single and double layered with Conventional RCC beam to the results of Finite Element analysis in Abaqus CAE software. The Rubber-mat was used in RCC beam to resists some plastic deformation and increase the load carrying capacity of beam by reducing the Plastic Strain in tension zone area where the flexural crack appears and increasing the Flexural Strength of Structural Beam.

Resumo em Inglês:

ABSTRACT The impact turbine equipment will be seriously disturbed in the high altitude, water temperature, sediment content and other environments in the plateau area, so that it can not run stably. In this paper, the plateau impact turbine model test bed and data acquisition system are designed. According to the standard of general test bed, the basic parameters of the turbine unit are determined by changing the specific speed method, and the working head of the centrifugal pump is set up to simulate the impact turbine by referring to the characteristics of the plateau water flow drop doing work to the turbine. The structure of torsion meter calibration device used in test bench calibration is designed. The efficiency test and runaway test of the turbine model are carried out on the test bench. The experimental results show that the test bench can effectively test the performance and hydraulic performance parameters of the turbine in the plateau environment, and the test accuracy meets the requirements of the turbine model IEC-60193, which provides test support for the performance research and application of the turbine in the plateau environment, and has important engineering application value.

Resumo em Português:

RESUMO A alvenaria estrutural é uma metodologia construtiva antiga e amplamente utilizada. Para avaliar o comportamento mecânico da alvenaria, é necessário conhecer as propriedades mecânicas dos materiais constituintes. Este trabalho tem como objetivo investigar comparativamente as propriedades mecânicas obtidas por meio de ensaios em blocos de concreto e os resultados obtidos através de ensaios em seus testemunhos, comparando a correlação entre ambos para validar a possibilidade de determinar essas propriedades utilizando testemunhos. Isso tornaria o processo menos invasivo na alvenaria a ser estudada. Para isso, foram realizados ensaios de compressão simples, tração na flexão, obtenção do módulo de elasticidade estático através do ensaio de compressão x deformação, além da determinação da massa específica. Os resultados obtidos com o ensaio em testemunho de blocos de concreto apresentaram variações: 1,42% para a massa específica, 7,58% para a resistência à compressão, 21,4% para a resistência à tração na flexão e 2,35% para o módulo de elasticidade. Essas variações indicam pouca divergência entre os resultados, o que sugere a viabilidade da utilização de testemunhos para a determinação das propriedades mecânicas de blocos de concreto.

Resumo em Inglês:

ABSTRACT Structural masonry is an old and widely used constructive methodology. To evaluate the mechanical behavior of masonry, it is necessary to know the mechanical properties of the constituent materials. This work aims to investigate comparatively the mechanical properties obtained by testing concrete blocks and the results obtained through tests in their cores, comparing the correlation between both to validate the possibility of determining these properties using cores. This would make the process less invasive for the masonry to be studied. For this, simple compression tests, flexural tensile strength, static modulus of elasticity through the compression x deformation test were performed, in addition to the determination of the specific mass. The results obtained with the concrete block core assay showed variations: 1.42% for specific mass, 7.58% for compressive strength, 21.4% for tensile strength in bending and 2.35% for modulus of elasticity. These variations show a little divergence between the results, which suggests the feasibility of using cores to determine the mechanical properties of concrete blocks.

Resumo em Inglês:

ABSTRACT This research aims to investigate the microstructure evolution and related mechanical properties of Mg-9.5Gd-0.8Zn-0.5Zr alloys with different Y contents (x = 0, 1, 2, and 3wt%). The effects of different heat treatment conditions on these alloys were investigated. The results show that the initial microstructure of the as-cast alloy without Y is composed of α-Mg matrix and Mg5Gd phase. Additional phases such as Mg24(Gd,Y)5 and Mg24Y5 appeared with the increase of Y content. After homogenization treatment, these phases are transformed into high temperature stable 14H-LPSO phase. It is noteworthy that the precipitation of the β′ phases in peak-aged alloys significantly enhances the strength, while the addition of Y enhances the plasticity. The peak-aged Mg-9.5Gd-0.8Zn-0.5Zr-2Y alloy exhibits the best mechanical properties, and the ultimate tensile strength, yield strength and elongation are 313MPa, 211MPa and 6.51%, respectively.

Resumo em Português:

Resumo A estabilização do solo com asfalto é uma técnica que pode melhorar as características mecânicas do solo, sendo uma opção viável tanto do ponto de vista econômico (reduzindo os custos com transporte de materiais) quanto ambiental (principalmente na fase construtiva, diminuindo as emissões relacionadas ao transporte e utilizando materiais locais, o que também reduz a exaustão de jazidas). Nesta pesquisa, foi utilizado um método de estabilização com baixos teores de asfalto e uma emulsão asfáltica de ruptura lenta. Analisou-se a influência da estabilização na ocorrência de shakedown. Os resultados demonstraram uma melhora no módulo resiliente (MR) e uma redução da deformação permanente (DP) do solo em comparação com o solo in natura, mas observou-se uma piora da DP em relação ao solo controle. O MR alcançou valores de 600 MPa no último ciclo de carregamento, enquanto a DP foi reduzida em aproximadamente 189%. Esses resultados indicam que a estabilização do solo com asfalto é uma técnica promissora para aplicações em pavimentação.

Resumo em Inglês:

ABSTRACT Soil stabilization with asphalt is a technique that can improve the mechanical properties of soil, being a viable option both economically (reducing transportation costs of materials) and environmentally (mainly in the construction phase, reducing emissions from material transportation by using local materials, and depleting fewer quarries). In this research, a stabilization method with low asphalt content and a slow-setting asphalt emulsion was used. The influence of stabilization on the occurrence of shakedown was analyzed. The results showed an improvement in the resilient modulus (MR) and a reduction in the permanent deformation (PD) of the soil compared to natural soil, but a worsening in PD compared to the control soil. The MR reached values of 600 MPa in the last loading cycle, and PD was reduced by approximately 189%. These results indicate that soil stabilization with asphalt is a promising technique for pavement applications.

Resumo em Inglês:

ABSTRACT Current research has focused on investigating substances that are less toxic and harmful to human health and the environment. In the context of natural compounds for corrosion protection, this study examined the incorporation of tannic acid into a nanoceramic conversion treatment for cold-rolled steel. The research was structured around three different treatment methodologies, in which nanoceramic conversion and tannic acid application were performed by immersion in aqueous solutions. The addition of tannic acid was evaluated before, during, and after the nanoceramic conversion process. These treatments were then compared with a standard nanoceramic treatment and a control sample prepared using only the surface cleaning method. The results indicated a notable increase in corrosion protection, especially when tannic acid was introduced before the nanoceramic conversion stage, resulting in a protection efficiency of 79.3% compared to the control sample and 37.5% compared to the standard nanoceramic treatment. Contact angle measurements and Raman spectroscopy suggested surface modifications, with the simultaneous formation of iron and zirconium oxides, as well as the complexation of ferric tannate. Consequently, the proposed treatments offer a promising alternative to traditional methods used in industry; however, more detailed studies are needed to validate these findings in real-world applications.

Resumo em Inglês:

ABSTRACT The study of the corrosion of buried structures becomes necessary as their use increases. This study aims to evaluate the corrosion of AISI 304 stainless steel samples inserted in three different types of soil (Neossolo, Cambisol and Latosol) with a forced and conventional acidic pH during a period of six months. The corrosion behavior of the stainless steel samples was verified through the potentiodynamic polarization curves and the corrosion potential. The results demonstrated that the Neossolo presented a lower corrosive potential in the six-month period analyzed in acidic and natural pH conditions. The samples in Ambisol and Latosol presented similar results in the acidic pH coding. The results did not vary significantly in soils under natural conditions due to the non-rupture of the passive Cr2O3 layer. All samples with an acidic pH presented surface corrosion pits. The study of the corrosion of buried structures becomes necessary as the use of these structures increases, especially in buried pipelines and water.

Resumo em Inglês:

ABSTRACT Internal combustion engines must be kept at a certain temperature in order to work efficiently. During the design of the engines, cooling systems are used to keep them in the temperature ranges determined. Water pumps are used in the engines for the circulation of the water used in the cooling systems. Failure of these pumps can cause enormous damage to the engine. In this study, the damage caused by the water pump of an engine operating according to the otto principle was investigated. In damage analysis studies, metallographic samples of the broken surfaces of the circulation pump were prepared. Spectroscopic analyses, metallographic analyses, and hardness measurements were made. Additionally, the solid model was drawn, and stress analyses were carried out using the finite element method. Spherical cementites were observed in optical microscope images of the material. Ferrite-rich regions were detected towards the inner parts of the material.In this study, it was observed that intergranular morphology coalescence occurred due to fatigue, but dense corrosion deposit was observed at the crack initiation. As a result, the fatigue strength of the material decreased due to some errors made during production and rapid breakage occurred due to the corrosive effect of the working environment.

Resumo em Inglês:

ABSTRACT Aluminium alloy (AA8050) matrix material is reinforced with various wt.% of Zirconia Toughened Alumina (ZTA) particle through powder metallurgy (P/M) technique. The even distribution of ZTA particles into the AA8050 matrix was confirmed by Scanning Electron Microscopy (SEM) analysis. The findings indicated that, hardness raised for the addition of ZTA particles up to 8 wt.%, after that, and decreased for the 12 wt.% of ZTA addition. The Compressive Strength (CS) of the composites was improved and the maxi-mum CS of 168 MPa was attained for AA8050-12 wt.% of ZTA composite. The dry sliding wear test has been performed by the pin-on-disc tribometer with considering four input parameters like wt.% of ZTA (R), Sliding distance (D), Sliding Velocity (V), and load (L). The Taguchi method was applied to detect the optimum parameters for obtaining less of the dynamic Coefficient of Friction (COF) and Wear Rate (WR) of the proposed composites. From the Analysis of Variance (ANOVA), it was revealed that wt.% of ZTA had the note-worthy factor which affects WR followed by ‘L’. Similarly, L and D have a significant role on COF. The worn surface morphologies have been analyzed by SEM and the formation of wear mechanisms was reported.

Resumo em Inglês:

ABSTRACT The mechanical and metallurgical properties of the AISI 316/AISI 410 stainless steel junctions are examined in this study employing TIG welding. The microstructural properties of the welds were examined, and their effects on joint integrity were evaluated by exposing them to different welding conditions. Strength-loving AISI 410 stainless steel and corrosion-resistant AISI 316 stainless steel were butt connected and put through various tests. The complicated interplay between alloy compositions and welding conditions was highlighted by the results, which showed significant differences in both mechanical strength and microstructure. The purpose of this study is to shed light on how best to weld different types of stainless steel alloys together. Experiments using TIG welding with varying current flows, welding speeds, and shielding gas flow rates were conducted to achieve this. The optimal method settings were determined by taking into account responses such as micro hardness and tensile strength. Their effects had been ascertained through the use of analysis of variance. Based on the GRA, the optimal set of settings was determined to be 120 amp welding current, 2 m/min welding speed, and 10 lit/min shielding gas flow.

Resumo em Inglês:

ABSTRACT The rolling of 3D curved parts based on arc-shaped rollers is a new and effective method for forming curved parts with double curvature. In this paper, the spherical parts are taken as an example, and the influence of sheet dimension on the rolling of 3D curved parts is studied for the first time. A series of numerical simulations and experiments are carried out with different sheet dimensions under the same maximum rolling reduction ratio. The effect of the length, width, and thickness of the sheet metal on the longitudinal bending deformation and material utilization of the formed spherical parts was investigated. Numerical simulation and experimental results show that the longitudinal bending deformation of the formed spherical part is not affected by the sheet length, and decreases with the increase of the sheet width, and decreases with the increase of the sheet thickness. The material utilization rate of the formed spherical part increases with the increase of the sheet length, decreases with the increase of the sheet width, and decreases with the increase of the sheet thickness.

Resumo em Inglês:

ABSTRACT Ultra high performance fiber reinforced concrete (UHPFRC) stands at forefront of modern construction materials, offering superior strength and durability. The removal of coarse aggregate aims to enhance the compactness and performance of the material, while alternative reinforcement mechanisms of Polypropylene fiber (PF) and hooked Steel fibers (SF) compensate for the absence of traditional fibers. Six mix designs M1 comprises 1% PF and 0.25% SF, M2 features 1% PF and 0.5% SF, and M3 incorporates 1% PF and 0.75% SF, M4 comprises of 1% PF and 1% SF, M5 of 1% PF and 1.25% SF and M6 with 1% PF and 1.5% SF. The mechanical behaviour of these mixes compressive, tensile, and flexural strength were assessed through extensive testing. The findings offer crucial insights into the mechanical performance of UHPFRC formulations that exclude coarse aggregates and traditional fibers, aiding in the optimization of mix designs and broadening the material’s application potential. This research advances sustainable construction practices which encourages the usage of materials with enhanced mechanical properties across various structural applications. Understanding the nuances of UHPFRC mixes without coarse aggregate and traditional fibers is paramount for driving innovation in the construction industry and meeting the demands of modern infrastructure projects.

Resumo em Inglês:

ABSTRACT Low-density concretes made with lightweight aggregates are known for their enhanced thermal insulation properties. Though the temperature resistance is better than normal concretes, lightweight aggregate concrete (LWAC) experiences significant structural degradation when subjected to extreme conditions, especially those exceeding temperatures of 400°C. Encompassing the safety and durability of structures, auditing the strength of LWAC subject to elevated temperatures is crucial. The present research aims to analyse the density, strength, and microstructural morphology of expanded clay aggregate concrete when subjected to elevated temperatures, particularly 100°C, 200°C, 400°C, and 800°C. Concrete mixes were prepared with crushed stone aggregates replaced with ECA at 0%, 50%, and 100% by volume. The mixes were then further modified by reinforcing the matrix with hybrid fibres at 1.5% (1% steel and 0.5% polypropylene) by volume. The cured specimens were exposed to elevated temperatures and then tested for their mass and strength properties. Notable mass loss was observed for all the mixes post-thermal exposure, and improvement in strength was observed for the mixes when exposed up to 200°C. Further exposure led to a strength degradation. The observed degradation is potentially connected to the complete disintegration of the microstructure, as seen in the Scanning Electron Microscopy (SEM) images.

Resumo em Inglês:

ABSTRACT The present worldwide scenario is characterized by a significant environmental challenge pertaining to the appropriate management of PU waste disposal. The potential utilization of hybrid composites in Structural applications has been the subject of investigation, wherein discarded PU and teakwood particles have been explored as viable filler materials. The present study focused on the fabrication of hybrid composites through the blending of different proportions of discarded PU and teakwood particles s with a polyester resin matrix. Subsequently, an analysis was conducted to evaluate the mechanical characteristics of these composites. The mechanical properties of the composites were evaluated by the utilization of tensile, flexural, and impact tests. The findings of this study indicate that the inclusion of discarded PU and teakwood particles in the hybrid composites leads to improved mechanical properties. Nevertheless, the mechanical properties saw enhancement only until a loading of 60wt% of PU and teakwood particles waste, beyond which they started to deteriorate. According to research findings, the incorporation of teakwood particles waste as filler into hybrid composites, together with PU, has been shown to enhance the resistance of these materials to environmental degradation. Consequently, this composite formulation presents an appealing choice for application in maritime environments.

Resumo em Inglês:

ABSTRACT The impact of combining two distinct fibers in concrete composites, focusing on the mechanical and fresh properties of the material. The concrete grade used is M40, and the composite is composed of steel and polymeric fibers in two different volume fractions. Steel fibers with an aspect ratio of 80, alongside fibrillated polymeric fibers, are incorporated into the mix. A slump test was conducted on the fresh concrete to assess the influence of both single and dual fiber additions on workability. The study further examines the mechanical characteristics of hybrid fiber-reinforced composites, including compressive strength, split tensile strength, and flexural strength. These results are compared to those of single-fiber composites to evaluate performance differences. A numerical approach is also employed to predict and analyze the behavior of the hybrid system. The synergy mechanism created by the combination of steel and polymeric fibers enhances the mechanical properties, while also contributing to a reduction in the self-weight of the concrete. The failure mode of the hybrid composite was found to be ductile, indicating improved energy absorption and flexibility in comparison to more brittle, single-fiber systems.

Resumo em Inglês:

ABSTRACT In this study, steel rebar corrosion owing to chloride intrusion was evaluated in 5-year marine environment. Seawater is used as the mixing water for the concrete, and the specimens were completely immersed in seawater over 5-year study period. The study was conducted in two phases: Phase 1 was the first 3-years, and the concrete was allowed to continue its chloride reaction along with the rebar, and the rebar was allowed to corrode without any external protection; constant monitoring through half-cell potential and destructive tests, such as rebar diameter loss, were measured to track the corrosion level. After 23% of dimentional loss in rebar due to corrossion, cathodic protection is activated through the control system installed. The cathodic protection occurred over a period of 2 years, which is phase 2 of this study; during this phase, the half-cell potential values and current density were measured for the full 2 years. The bimetallic corrosion system reduces the steel rebar corrosion. Hence, zinc acting as the sacrificial anode provides protection to the steel rebar. The half-cell potential and current density values showed that the sacrificial anode provided efficient cathodic protection, thereby reducing corrosion and failure of the steel bar.

Resumo em Inglês:

ABSTRACT This research focuses on the fabrication and characterization of Fiber Metal Laminates reinforced with 5% BaSO4 nanoparticles for automotive applications. Eight distinct samples were produced using synthetic fibers (Kevlar, carbon, and glass fiber), natural abaca fiber, and an aluminum mesh (AL 1100) embedded in an epoxy resin matrix. Mechanical testing based on ASTM standards showed significant improvements in tensile, flexural, and impact strength. Kevlar fiber-reinforced Fiber metal laminates with BaSO4 nanoparticles exhibited the highest tensile strength at 18.27 kN, a 40% increase compared to non-reinforced fiber metal laminate. Flexural strength increased by 44% for Kevlar-reinforced fiber metal laminates, reaching 2.88 kN. Impact strength analysis revealed that nanoparticle-infused FMLs maintained superior energy absorption, with the Kevlar-reinforced Fiber metal laminates absorbing 90 J. Morphological analysis using Scanning Electron Microscopy confirmed enhanced microstructural integrity, with reduced void formation and better fiber-matrix adhesion in the nanoparticle-reinforced laminates. These results suggest that BaSO4 nanoparticles significantly improve the mechanical performance and structural integrity of fiber metal laminates, making them suitable for high-performance automotive components such as body panels and structural reinforcements.

Resumo em Inglês:

ABSTRACT The Cactaceae family is a suitable alternative for future sustainable development in the construction industry. In addition to being a renewable raw material, these plants grow with ease and are extremely adaptable to the most diverse and rigorous climates and poor soil. The Cereus jamacaru DC. has a woody structure that is unknown and, consequently, unexplored. This research aimed to characterize the secondary xylem of cactus and to evaluate its use in the development and characterization of lightweight bio-concrete. The anatomical properties were used characterized. The chemical composition, crystallographic structure thermogravimetric analysis was evaluated. To produce bio-concrete, the wood was washed in hot water, and flow table and uniaxial compression tests were performed. The results indicate that the species has a high extractive content and a low density. The bio-concretes produced are lightweight and show promising results for the use of C. jamacaru wood in the construction industry. The combination of bioconcrete, with its sustainable properties, and lignocellulosic reinforcements, which provide greater strength and lightness, results in a material with unique and advantageous characteristics. Possible applications include non-structural elements such as walls, cladding and partitions. And in low-load structural elements such as slabs and pillars.

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ABSTRACT The advancement of Wire EDM technology has provided a robust solution for machining hard-to-cut materials like Duplex Stainless Steel (DSS), which is widely utilized due to its superior strength and corrosion resistance. However, optimizing the machining process to achieve efficient material removal while maintaining high surface quality and accuracy remains challenging. This study aims to refine the Wire EDM process parameters—Pulse Time, discharge current, and travel speed—to optimize Material Removal Rate (MRR), surface roughness(Ra), and kerf width. Employing Response Surface Methodology (RSM), this research developed a predictive model to analyze the interactions between these parameters and their collective impact on machining outcomes. The experimental design was based on a Taguchi L27 orthogonal array, facilitating a detailed statistical analysis of the effects. Results indicated that travel speed significantly influences MRR, whereas Pulse Time predominantly affects (Ra). Optimizations led to an MRR improvement of up to 15%, reduced (Ra) by approximately 20%, and decreased kerf width by around 10%. The study concludes that precise control of EDM parameters significantly enhances machining efficiency and quality, underscoring the model's effectiveness in industrial applications for DSS.

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ABSTRACT Metal matrix composites (MMCs) offer inherent advantages, including higher stiffness, strength, high-temperature resistance, and creep resistance than polymer composites. These inherent properties make MMCs highly desirable for applications in industries such as automotive and aerospace. In this study, MMCs were fabricated with different percentages of zirconium boride (ZrB2) micro-powder using the stir casting process and then welded through Friction Stir Welding (FSW). The metallographic analysis of the weldments confirmed the defect-free weld joints. Tensile and hardness tests revealed that the tensile strength and elongation percentage increased with the addition of ZrB2 micro-particles. This trend was consistent in both base and welded samples. The welding process achieved defect-free joints with efficiencies of 81.1%, 79.2% and 77.4% for materials with 2.5%, 5.0%, and 7.5% micro powder, respectively. Furthermore, Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) tests conducted in a corrosive environment showed that the corrosion resistance of the base MMC samples improved after the addition of ZrB2 microparticles, and all welded samples exhibited enhanced corrosion resistance compared to their respective base materials. The MMC with 7.5% micro powder showed higher corrosion potential, 0.237 v and lower corrosion current, 8.5 × 10−7 mA/cm2 which represents the high corrosion-resistant property of the material.

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ABSTRACT The knowledge of the residual stresses generated in the welding process is especially important in the performance and service life of the welded structures and components. In this context, the present work aims to study the residual stresses generated in welded joints of advanced high strength steel (22MnB5), with Fe-Zn alloy coating, called GA (galvannealed), utilizing the resistance welding process. Residual stresses were experimentally analyzed using X-ray diffraction, employing the sen2psi technique. Vickers microhardness analyses were conducted, and the obtained measurements were incorporated into mathematical formulations to estimate the dislocation density in the analyzed region, employing a model based on microhardness measurements. Microstructural characterizations were carried out using optical microscopy (OM) and scanning electron microscopy (SEM), correlating with the residual stress results. The dislocation density results were approximately ρt = 7.42 × 1015 m2 for the weld metal and 7.05 × 1017 m2 for the base metal. The residual stress indicated compressive values with mean measurements ranging from 250 to 450 MPa, accompanied by hardness values spanning from 200 to 600 HV. These results demonstrate that the proposed technique holds promise for dislocation density evaluation.

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ABSTRACT This study's primary goal is to examine how brick type and power of mortar affect the strength of the prism masonry. The research further aims in evaluating various parameters influencing MCS. This study delves deeply into the findings of an investigation into the impact of several factors on prism strength, including strain at peak stress, h/t ratio of the prism, volume percentage of brick, modulus of elasticity and stacked and staggered bricks. A framework to calculate prisms' compressive strength is being devised based on regression analysis of experimental results. Regarding FLGQ bricks and Country burnt bricks, suggested model-based prediction has an accuracy of 98% and 66.86%, respectively. This demonstrates how well the suggested model works to forecast the prism MCS. This study also looks at the other characteristics of FLGQ brick and rural burnt clay bricks, as well as their uniaxial monotonic compressive stress-strain behaviour.

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ABSTRACT Heat engines are considered for various characteristics, such as durability, performance, and efficiency, to reduce the life cycle cost. The most effective gas turbines tend to make use of more recent developments in cooling and material mechanisms by switching to motor working cycles that use a significant portion of peak turbine inlet temperature ability over the whole working cycle. “Thermal Barrier Coatings (TBC)” carry out the crucial task of isolating portions of petrol generators also plane motors working at high temperatures. TBC is applied on metallic components that are thermally heavily loaded, such as those found in gas turbines. The efficiency of the process is increased by using the TBC, which boosts the process temperature. In this experiment, gadolinium zirconate (Gd2O7Zr2) is administered using the plasma arc method and test blends like B10, B20 and B30 blends were prepared by using waste transformer oil and nano additive and results depict that BTE increases of 1.2% than diesel and also shows lower emissions. Therefore, it is concluded that the TBC-operated CI engine with biodiesel blend shows a positive approach in both performance and emission.

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ABSTRACT Metal matrix composites (MMCs) are excellent for a variety of applications due to their increased mechanical qualities. MMCs' ability to reduce structural weight and consequently fuel consumption is especially appealing for usage in the ground transportation and aviation sectors. In this study, AA2017 strengthened with Zirconium diboride (ZrB2) was produced via stir-casting [SC] route. The reinforcement particle ZrB2 was mixed in various weight percentages 0, 5, 10 and 15. According to ASTM standards, the cast samples underwent mechanical characterization such as micro hardness and tensile tests as well as scanning electron microscopy (SEM) analysis. The SEM analysis witnessed the even dispersal of ZrB2 particles with AA2017 matrix with lesser agglomerations. The mechanical testing’s results showed improved properties and it was achieved for AA2017-15wt.% ZrB2 synthesized composites. Microhardness testing revealed an increase of around 101 VHN (40.28%) from the base as-casted alloy. Also the ultimate tensile strength (UTS) raised around 155 MPa (59.79%) from the as casted alloy.

Resumo em Português:

RESUMO A resistência mecânica de concretos e argamassas são influenciados pelas características dos agregados, incluindo forma, composição e rugosidade. O objetivo deste trabalho é investigar a influência da rugosidade de agregados graúdos reciclados na aderência com a argamassa cimentícia. A rugosidade dos agregados foi variada através de tratamento mecânico e lixamento manual para obtenção de diferentes níveis e foi quantificada através da microscopia confocal a laser. Através do método de imersão em argamassa, desenvolvido nesse estudo, foi analisada a zona de transição interfacial visualizada por meio da microscopia eletrônica de varredura. Os resultados indicam que o tratamento mecânico deve ser realizado de forma controlada para garantir o equilíbrio entre remover a argamassa aderida e não gerar uma superfície excessivamente rugosa que comprometa a interação com a pasta cimentícia. Concluiu-se que a topografia da superfície é um fator determinante para a aderência pasta-agregado e melhoria no comportamento mecânico do concreto fabricado com resíduo de construção e demolição. Rugosidades moderadas, com vales e depressões bem definidos e alternados, favorecem a penetração da pasta cimentícia e criam uma ligação interfacial mais densa.

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ABSTRACT The mechanical strength of concrete and mortars is influenced by the characteristics of the aggregate, including shape, composition and roughness. Recycled aggregates have a more porous surface and variable composition compared to natural aggregates, contributing to the interlocking of the system and increasing the transition area between the paste and the aggregate. The objective of this work is to investigate the influence of the roughness of recycled coarse aggregates on the adhesion with cementitious mortar. The roughness of the aggregates was varied through mechanical treatment and manual sanding to obtain different levels, and it was quantified using laser confocal micoscopy. Using the mortar immersion method developed in this study, the interfacial transition zone was analyzed through scanning electron microscopy. The results indicate that mechanical treatment should be performed in a controlled manner to ensure a balance between removing adhered mortar and not creating an excessively rough surface that compromises the interaction with the cement paste. It was concluded that surface topography is a determining factor for paste-aggregate adhesion and improvement in the mechanical behavior of concrete made with construction and demolition waste. Moderate roughness, with well-defined and alternating valleys and depressions, favors the penetration of the cement paste and creates a denser interfacial bond.

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RESUMO Os geopolímeros são materiais que apresentam alta resistência inicial à compressão, além de apresentarem resistência à altas temperaturas, a sulfatos e a ácidos. Porém, é um material cerâmico de comportamento frágil. Para compensar tal fragilidade, diversos tipos de fibras têm sido utilizadas. No presente trabalho, compósitos geopoliméricos reforçados com fibras de sisal foram produzidos e ensaiados à tração direta. Foram avaliadas duas diferentes distribuições de fibras contínuas e alinhadas: fibras distribuídas longitudinalmente e fibras distribuídas a 45°, em ambos os casos foram utilizadas uma fração volumétrica de 3% de fibras. O comportamento de deformação e fissuração foram analisados pela técnica de Correlação de Imagem Digital (CID). Os resultados encontrados foram comparados com outros resultados presentes na literatura, demonstraram similaridade com os estudos analisados. Os compósitos apresentaram comportamento strain-hardening com a formação de múltiplas fissuras, com o aumento da resistência após a formação da primeira fissura. Os compósitos com fibras distribuídas longitudinalmente apresentaram melhor desempenho, demonstrando que o desempenho dos compósitos depende da orientação de distribuição das fibras em relação ao carregamento aplicado.

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ABSTRACT Geopolymers are materials that present high initial compressive strength, in addition to presenting resistance to high temperatures, sulfates and acids. However, it is a ceramic material with brittle behavior. To compensate for such fragility, several types of fibers have been used. In the present work, geopolymer composites reinforced with sisal fibers were produced and tested under direct tension. Two different distributions of continuous and aligned fibers were evaluated: fibers distributed longitudinally and fibers distributed at 45°, in both cases a volume fraction of 3% of fibers was used. The deformation and cracking behavior were analyzed by the Digital Image Correlation (DIC) technique. The results found were compared with other results present in the literature, demonstrating similarity with the studies analyzed. The composites presented strain hardening behavior with the formation of multiple cracks, with an increase in resistance after the formation of the first crack. Composites with longitudinally distributed fibers showed better performance, demonstrating that the performance of composites depends on the orientation of fiber distribution in relation to the applied load.

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ABSTRACT The present research analysis the Electrical Discharge Machining parameters of reinforced magnesium composite. Through stir cast method, we synthesized the AZ61 magnesium alloy composite with varying weight percentages of silicon nitride (Si3N4) particles (0%, 4%, 8%, and 12%). This study fills a significant research gap in the Electrical Discharge Machining (EDM) machining of magnesium composites and optimizes parameters. The analysis involved machining the synthesized samples using the EDM process to calculate surface roughness (Ra) and Metal Removal Rate (MRR). Through advanced techniques such as analysis of variance (ANOVA) and L-16 design, we identified the optimal EDM machining parameters that led to superior machining surface quality and improved MRR. Based on ANOVA, the Pulse off time (Toff)/Pulse on time (Ton) and composites identified as 88%, 8%, and 2% influencing the MRR and 33%, 22% and 16% influences to the surface roughness of machined composite sample. The results help to clarify how particular parameter combinations affect machining results, allowing for more accurate control for enhanced performance.

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ABSTRACT This work focuses on investigating the significant enhancement in wear properties of AA6061 alloy hybrid composite through the inclusion of graphite and hafnium diboride (HfB2) particles. AA6061 alloy, largely deployed in aviation and automobile sectors because of its high corrosion and in wear resistance. Stir casting method was adopted to create hybrid composites by adding different percentages of graphite and HfB2 particles into the AA6061 matrix. SEM and Microhardness were used to examine the microstructure of the resultant composites to verify the even dispersal of reinforcing particles and the alloy's hardness. To compare the tribological performance of the hybrid composites to that of the base AA6061 alloy, wear experiments were conducted under different loading conditions. Results revealed a considerable improvement in wear resistance with the inclusion of 5% of graphite particles with 15% of HfB2 particles. Hard HfB2 particles improved load-bearing and abrasion resistance. The synergistic effect of graphite and HfB2 resulted in a hybrid composite with significantly lower wear rates and friction coefficients contrast to the base AA6061 alloy. This work findings highlights the potential of hybrid reinforcement strategies in developing advanced materials with enhanced tribological performance making it promising for suspension components and roof rails in automotive sectors.

Resumo em Inglês:

ABSTRACT Modern structural issues require multi-functional concrete, and demand for it is enriched. The advancement of nano engineering technology plays a major role in the cementitious materials namely flyash, silica fume and graphene oxide. In this research varying percentages from 0 to an increment of 0.01% upto 0.05% of graphene oxide and 20% of flyash and silica fume together is used by weight of ordinary Portland cement to obtain high strength. To unravel the complex flexural behavior of concrete structures by integrating static load tests and the best mix is compared with advanced Finite Element Analysis (FEA) techniques, specifically utilizing ANSYS. The study investigates the structural response under static loading, focusing on vital parameters such as load deflection, ductility factor, stiffness factor, energy absorption capacity, and energy index. The examination of these factors provides comprehensive insights into the material's deformation characteristics and resilience in flexural conditions. The incorporation of innovative materials fly ash, silica fume, and graphene oxide into the concrete matrix are potential to enhance concrete properties, and their impact on flexural behavior. The 0.04% of graphene oxide is superior in all aspects flexural behavior and it is compared with FEA model (ANSYS).

Resumo em Inglês:

ABSTRACT Hardened concrete is stable in compression and weak in tension. To address this predicament, we introduce reinforcements in the concrete. It is a known fact that glass products are globally viable non-biodegradable environmentally hazardous material and Sisal fiber on the other hand is a ubiquitcous natural fiber. Glass substances when ground to powder particles behave like PPC substances capable of producing a budgetary and sizable plain concrete when replaced partially for cement. Sisal fiber in concrete on the other hand results in improved compressive strength on a smaller scale and tensile strength on a larger scale. a the This venture compares a trial specimen using Na2CO3 treated sisal fibers and glass powder replacement at partial level for binder with conventional M20 concrete. The strength and durability aspects of the novel specimen were studied and compared with that of the conventional specimen. Keeping 15% of glass powder as partial substitution percentage for cement, sisal fiber is added in varying proportions achieving 1.5% as the optimum addition value. It was concluded that the Sisal fiber-glass powder composite at the optimum value enhanced the strength and durability properties when analogized to the other specimens.

Resumo em Inglês:

ABSTRACT This study focuses on developing hybrid polymer composites by incorporating cashew nut shell liquid (CSNL) and aluminum powder into LY556 epoxy resin. The objective was to enhance the material's mechanical properties, specifically tensile strength, thermal stability, and flexural strength, while promoting sustainability using agricultural by-products. The materials were blended in various proportions with aluminum particles of micron and nano sizes to identify the optimal composition. A thorough characterization was performed using tensile and flexural testing, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Results indicated that a composition of 2.5% aluminum powder and 30% CSNL yielded significant improvements in tensile and flexural properties, achieving tensile strength values of 64 MPa and a flexural strength of 45 MPa. SEM analysis revealed a homogenous distribution of aluminum particles, while FTIR confirmed successful bonding between the components. These findings suggest that the integration of CSNL and aluminum particles into epoxy resin provides a feasible method for producing sustainable hybrid composites with enhanced mechanical and thermal properties.

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ABSTRACT In this paper, a total of 12 groups of thin plate-shaped specimens were designed and produced to investigate the flexural behavior of HSSWM-PUC composite materials through four-point bending tests, considering the effects of parameters such as rubber-powder ratio, reinforcement ratio and specimen width on the flexural behavior of the materials. Based on the test study, flexural load capacity calculations and finite element parametric analysis of HSSWM-PUC composite materials were carried out. As the reinforcement ratio of HSSWM increased, the ultimate load of the specimen increased accordingly. The ultimate load of the specimen with the highest reinforcement ratio was 8.99 kN, which was 63% higher than that of the specimen with the lowest reinforcement ratio. Increased width of thin plate-shaped specimens can improve the flexural load carrying capacity of HSSWM-PUC composite materials while increasing the flexural stiffness of the composite materials. When the width of the specimen increased from 70 mm to 130 mm, the ultimate load increased by 115%, and the maximum deflection decreased by 55%. Based on the simplified intrinsic relationship model of the materials, the flexural load capacity calculation formula of thin plate-shaped specimens of HSSWM-PUC composite materials was proposed. Through finite element analysis, the change rule of the bending performance of the thin plate was investigated, and the test results were effectively verified. Meanwhile, this paper proposed the optimisation direction of PUC mixing ratios to support the design and project implementation of HSSWM-PUC composite materials in the future.

Resumo em Inglês:

ABSTRACT In this paper, a total of 15 sets of dumbbell shaped specimens were designed and fabricated. The flexural properties of high strength steel wire mesh-polyurethane cement (HSWM-PUC) composites were investigated by uniaxial tensile tests. Consider the effect of parameters such as specimen width, adhesive powder ratio, recuperation time and specimen depth on the stretching of the material. The results of the test showed that: The adhesive powder ratio significantly affects the tensile strength and ultimate tensile strain of HSWM-PUC composites. The ultimate tensile strain of the specimen with a adhesive powder ratio of 1.33 was 25% higher than that of the specimen with a adhesive powder ratio of 0.75. The specimen with a adhesive powder ratio of 0.75 showed an increase in tensile strength of about 11% over the specimen with a adhesive powder ratio of 1.33. Increasing the adhesive powder ratio improves the ductility of the material but reduces the tensile strength. The recuperation time has a large effect on both tensile strength and the ultimate tensile strain of HSWM-PUC composites. SWM-PUC dumbbell shaped specimens can reach 63%, 72% and 91% of their tensile strength at 28 d age after 6 h, 12 h and 1 d of conditioning, respectively. The section width and specimen depth have little effect on the ultimate tensile strain of the composites. Propose directions for optimization of polyurethane cement mixing ratios. Provide a basis for material design and engineering application of HSWM-PUC composites.

Resumo em Inglês:

ABSTRACT This study examines the impact of adding nitrogen (N+) to the surface of 42CrMo4 steel on its structural and mechanical properties. The specimens (T2, I2) were nitrided first at 580°C for 13 hours, and then at 560°C to remove oxides. Later, we compared them with the untreated specimens (T1, I1) to assess the impact of thermochemical treatment. The mechanical properties and fracture behaviors were examined and analyzed using Vickers microhardness, unidirectional tensile, and Charpy U tests. The nitrogen and carbon profiles in the nitrided layer were predicted by simulating the nitriding process. Findings show a progressive decrease in nitrogen content from 0.6 to 0 wt.%, unlike the carbon which increases to 0.4 wt.% after 414 μm. Besides, the microscopic observations show a dense white layer of nitrides (T2, I2), while the untreated specimens exhibit a ferrite and pearlite microstructure. The X-ray diffraction (XRD) analyses show the formation of iron and chromium nitrides (ε-Fe2-3N, γ-Fe4N, γ-(Fe, Cr) N4) in the surface layer, accompanied by a decrease in pure α-iron. The nitrided 42CrMo4 steel is characterized with an increase in the lattice parameter, followed by a reduction in the grain size. Moreover, the maximum hardness of approximately 603 HV in the nitrided layer decreased to around 215 HV at a depth of 414 μm. The uniaxial tensile test reveals ductile behavior at the core of the nitrided steel, unlike the surface, which is hard and fragile. Finally, the mechanical properties improve after plasma nitriding, increasing the elasticity modulus to E = 401700 MPa and the tensile strength to Rm = 1219.7 MPa.

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ABSTRACT The efficiency and durability of engineering systems are heavily influenced by material interactions and resulting friction and wear conditions. This is crucial for cold forming tools for aluminum alloys, where ceramics like TiN, CrN, and DLC are used to enhance tool lifespan. This study assesses less common ceramics such as Si3N4, Al2O3, and ZrO2 compared to high carbon steel (SAE52100) in a sphere-on-plate contact with 1100 aluminum under dry conditions. The goal is to identify superior ceramic coatings to improve forming processes and productivity. Tests were performed with a 10 N load, 2 Hz motion frequency, and 25 mm amplitude over 10 m. Tribological performance was evaluated through friction and wear coefficients and wear mechanisms. The results indicate that the choice of counter-body material has a minimal effect on the friction and wear coefficients. Among the tested materials, SAE52100 exhibited the highest friction (1.0042) and wear rate (1.345×10−5mm3/m·N), while Al2O3 demonstrated the lowest friction (0.9456) and wear rate (0.950×10−5mm3/m·N). Friction and wear coefficients decreased moderately with increased hardness, highlighting its role in tribosystem behavior. Despite this, wear mechanism analysis suggests minimal influence from counter-body material, as galling was observed under all conditions.

Resumo em Inglês:

ABSTRACT This research focuses on the effectiveness of strengthened unreinforced masonry (URM) wallettes using ferrocement geopolymer mortar (FCGPM). URM structures are vulnerable to earthquake forces and retrofitting methods are often needed to enhance their strength and seismic resistance. The FCGPM was employed as a strengthening material due to its high tensile strength and durability. Unreinforced Masonry structures are the general technique of building construction in the olden days. Those buildings are even being used till now. Also, even now residential buildings are being constructed because of the cost effectiveness of the unreinforced masonry construction compared to framed structure. The performances of such structures are poor during earthquakes. To improve the shear strength of those structures to have better performance for the seismic load it is necessary to strengthen the existing structure. In this study, using ferrocement geopolymer mortar to enhance the strength of the structure. The Welded Wire Mesh (WWM) of size 2.07 mm and 3.2 mm of spacing 25 mm and 50 mm respectively is this research used. The geopolymer mortar of binder to fine aggregate ratio 1:3 is used for strengthening. The URM strengthened with WWM of 50 mm spacing shows the highest shear strength and modulus of rigidity.

Resumo em Inglês:

ABSTRACT An increasing amount of waste is being disposed of as a result of growing industrialisation, endangering the environment. In the building industries of all the fly ash-producing nations, fly ash is used in structural and non-structural concrete in a variety of ways. Practically, high-volume flyash consumption is a significant advancement. Thus, an inquiry into high calcium fly ash-based geopolymer composites is started through this investigation, using class C fly ash obtained from the Thermal Power Station of Neyveli Lignite Corporation as a quantum waste. Geopolymer composites with diverse molarities for M30, M35 and M40 were experimented with characteristics of compressive, split tensile, flexural, water absorption, and rapid chloride ion penetration tests and correlated with standard concrete. The outcome established that a geopolymer composite with 12 molarity blended with crushed stone sand and pond ash bottom ash recycled coarse aggregate salvage marble coarse aggregate was optimal in characteristics. Investigation reveals that water absorption is relatively minimal in geopolymer composites compared to standard concrete. RCPT shows the geopolymer concrete has excellent chloride resistance over prolonged curing time. This study sees an opportunity to evaluate the effects of employing alternatives for both fine and coarse materials. Here, fly ash completely replaces the cement.

Resumo em Inglês:

ABSTRACT The increasing demand for sustainable materials has sparked growing interest in natural fiber composites, such as bamboo-reinforced polymers, due to their renewability, cost-effectiveness, and favorable mechanical properties. This study evaluates the mechanical performance of bamboo-reinforced composites fabricated using epoxy and polyurethane matrices, highlighting their potential as eco-friendly alternatives to synthetic composites. Bamboo's high strength-to-weight ratio and compatibility with polymer matrices make it a promising reinforcement material for structural applications. Experimental results showed significant improvements in tensile and flexural properties. Unidirectional bamboo-epoxy composites achieved a tensile strength of 125 MPa, a 25-fold increase compared to the pure epoxy matrix (5 MPa). The modulus of elasticity also increased from 20 MPa for pure polyurethane to 4,020 MPa in unidirectional bamboo-polyurethane composites. Flexural strength improved markedly, with unidirectional bamboo-epoxy composites reaching 80 MPa compared to 6 MPa for the pure matrix. Microstructural analysis indicated enhanced fiber-matrix adhesion and optimized fiber orientation as key factors contributing to the improved performance, while voids and fiber pull-out limited further enhancements. These findings demonstrate bamboo composites' viability as sustainable materials with competitive mechanical properties. This study lays the groundwork for future optimization and broader industrial adoption of bamboo-reinforced composites.

Resumo em Inglês:

ABSTRACT The laser brazing technology for TC4 titanium alloy using a Ti-based amorphous alloy as brazing filler metal was studied. Results show that laser brazing of TC4 titanium alloy can be achieved by using a Ti-based amorphous alloy, and a continuous and stable brazed joint without welding defects can be obtained. The microstructure comprises broken β-Ti dendrites dispersed on the amorphous alloy matrix, and columnar crystals are formed on both sides near the interface of the base metal. In the brazing process, the Zr element in the liquid filler metal diffuses to the TC4 base metal at a depth of about 50 μm. The hardness of the brazed zone is about 540 HV, which is much higher than that of the base metal at 320 HV. The tensile strength of brazed joint is about 960 MPa, and the specimen fractured on TC4 base metal.

Resumo em Inglês:

ABSTRACT The increase in hospital-acquired infections (HAIs) associated with medical devices underscores the need for antimicrobial coatings. This study aims to compare the antimicrobial efficacy, biocompatibility, ion release, and durability of silver nanoparticles, copper coatings, and zinc oxide nanostructures as coatings for medical devices. Coatings were prepared and characterized, with efficacy tested against E. coli and S. aureus via inhibition zone measurements. Silver demonstrated the highest antimicrobial effect, with inhibition zones averaging 90%, while copper and zinc oxide showed moderate efficacy, averaging 80% and 70%, respectively. Biocompatibility, assessed using human fibroblasts in an MTT assay, showed the highest cell viability with zinc oxide, followed by copper and silver. Durability tests under simulated physiological conditions indicated that copper and zinc oxide retained over 90% structural integrity, while silver showed greater degradation. Ion release profiles highlighted silver’s rapid ion release, ideal for short-term antimicrobial activity, while copper and zinc oxide showed steady, sustained ion release. These findings suggest silver’s efficacy for immediate infection control, while copper and zinc oxide offer balanced long-term safety and durability, making them suitable for extended applications in medical devices.

Resumo em Inglês:

ABSTRACT Nanomaterials have emerged as transformative agents in enhancing the thermal performance of heat pipes, which are vital components in modern cooling systems for electronics, aerospace, and renewable energy applications. This study explores the use of nanofluids containing silver (Ag), aluminum oxide (Al2O3), and multi-walled carbon nanotubes (MWCNTs) as working fluids in heat pipes, comparing their performance against deionized (DI) water under varying heat inputs, inclination angles, and filling ratios. A copper heat pipe with a stainless-steel mesh wick structure was used in controlled experiments, systematically evaluating thermal resistance and heat transfer coefficients. Results revealed significant improvements in thermal performance with nanofluids. MWCNT nanofluid demonstrated the highest thermal conductivity increase (40%), while Al2O3 and Ag nanofluids exhibited 30% and 17.6% improvements, respectively. Optimal performance was achieved at a filling ratio of 80% and a heat input of 60 W, with thermal resistance reduced to 0.87 K/W for MWCNT nanofluid, compared to 1.65 K/W for DI water. These findings underscore the potential of nanomaterials to revolutionize thermal management systems, providing insights into designing more efficient and reliable heat transfer solutions for high-performance environments. Future work will address nanofluid stability and cost-effectiveness in industrial applications.

Resumo em Português:

RESUMO A impressão 3D vem sendo cada vez mais utilizada pela indústria para fabricação de peças protótipos e produção em pequena escala devido a vantagens como baixo custo e possibilidade de produzir geometrias complexas. O Poliácido Lático (PLA) é um dos materiais mais utilizados por essa tecnologia, e apesar de existirem estudos que mostram como as propriedades mecânicas de peças impressas em PLA são afetadas por parâmetros de impressão, existe pouca informação sobre resistência a flexão e estatística/variabilidade dos modelos. Este trabalho relata um teste piloto e uma pesquisa experimental que buscou gerar modelos estatísticos que descrevam o comportamento de peças impressas de PLA nos padrões concêntrico e linha ±45°. São apresentadas equações de regressão com intervalos de predição para preenchimentos de 20, 40, 60, 80 e 100%, que mostraram uma tendência linear para o padrão concêntrico e um comportamento quadrático para o padrão linha ±45°. Na terceira parte do estudo, as curvas foram validadas com amostras impressas com preenchimentos de 30, 50, 70 e 90%. A variabilidade dos modelos foi avaliada através de um procedimento de reamostragem e dados revelaram que as maiores variações foram obtidas para o preenchimento linha após retiradas 8 amostras aleatoriamente. No geral, os resultados mostraram maiores valores de resistência a flexão para o preenchimento concêntrico do que para o linha ±45°.

Resumo em Inglês:

ABSTRACT The process of 3D printing of components has been increasingly adopted by the industry due to advantages such as low cost and the possibility to produce complex geometries. Polylactic Acid (PLA) is one of the materials most used by this technology and although there are some studies that show how the mechanical properties of PLA 3D printed components are affected by the printing parameters, there is little information about flexural resistance and statistical/variability. In this work, regression models were used to describe the behavior of 3D printed specimens in PLA for the concentric and linear ±45º fill patterns. Equations with prediction intervals are presented for the fill percentages of 20, 40, 60, 80 and 100% and show a linear tendency for the concentric pattern and a quadratic behavior for the linear ±45º pattern. In the third part of the study, these statistical curves were validated with samples printed with fillings of 30, 50, 70 e 90%. Model variability was evaluated through a re-sampling procedure and data reveals the highest variations were obtained for the linear ±45º model after 8 samples were randomly removed. In general, results showed the concentric pattern has higher flexural resistance than the linear ±45º pattern.

Resumo em Inglês:

ABSTRACT This study investigates the incorporation of rubber granules (RG) into epoxy composites at volume fractions of 10%, 20%, 30%, 40%, and 50%. The objective is to enhance impact toughness and thermal insulation while addressing the trade-offs in mechanical properties. Composites were fabricated using a manual molding technique, and mechanical properties were assessed through tensile, compressive, bending, and impact tests, alongside thermal conductivity and FTIR analysis. Results indicate that adding RG significantly improves impact strength and flexibility, with maximum elongation at break observed at 50% RG. Tensile strength and hardness were reduced proportionally with RG content, however, the thermal conductivity decreased, i.e., the obtained materials had a better insulation property. Chemical shifts caused by molecular interactions after the impact testing were revealed by FTIR analysis. Based on these findings, we conclude that RG-reinforced epoxy composites are good candidates for energy absorption and thermal stability. Nevertheless, the lower stiffness and strength restrict their use in load bearing structures, posing a demand for the hybrid reinforcements for the broader industrial applications.

Resumo em Inglês:

ABSTRACT As the demand for energy-efficient building solutions grows, innovative materials such as thermoplastic bricks have emerged as potential alternatives to traditional construction materials. This study investigates the thermal insulation properties of thermoplastic bricks and their suitability for enhancing energy efficiency in modern architecture. Various thermoplastic polymers, including polypropylene (PP), polyethylene (PE), and polyvinyl chloride (PVC), were analyzed to determine their effectiveness as insulating materials. The research also explores different fabrication techniques, such as injection moulding and extrusion, to understand their impact on the thermal performance of the bricks. Experimental evaluations were conducted using standardized thermal testing methods to measure the heat transfer characteristics of the brick samples. The results demonstrated that PVC bricks, especially those manufactured through injection moulding, exhibited the lowest thermal conductivity, thereby providing superior insulation. The study highlights the importance of material selection and processing methods in optimizing the thermal properties of thermoplastic bricks. In addition to their insulation capabilities, thermoplastic bricks offer environmental and economic benefits. They can be produced from recycled plastics, supporting sustainable building practices and reducing construction costs. This versatility, combined with their lightweight and ease of installation, positions thermoplastic bricks as a viable option for both residential and commercial applications. The findings of this study suggest that thermoplastic bricks can significantly contribute to reducing energy consumption in buildings, aligning with global efforts towards sustainable and energy-efficient construction. Further research is encouraged to explore the long-term performance and broader applications of these innovative building materials.

Resumo em Inglês:

ABSTRACT The primary objective of this study is to enhance surface coating characteristics and reduce the dilution rate of AZ61 magnesium alloy coated with Stelcar alloy powder through laser cladding. A Taguchi (L16) orthogonal experimental design employed to analyze the effects of scanning speed, laser power, powder feed rate, and gas flow on wear volume, dilution rate and micro-hardness. Signal-to-noise ratios were calculated for each parameter to identify their individual effects on the responses. The findings indicated that powder feed rate predominantly influenced wear volume, accounting for 88.18% of its variation, while scanning speed has the highest influence on dilution rate (73.20%), and laser power significantly affected micro-hardness (84.60%). The optimized processing parameters were identified as a scanning speed of 11 mm/s, a laser power of 1.3 kW, a powder feed rate of 40 g/min, and a gas flow rate of 380 L/h. These parameters yielded a minimum wear volume of 0.8427 mm3, a dilution rate of 18.21%, and a maximum micro-hardness of 678.07 HV. This study utilized grey relational analysis to determine the optimum processing parameters, which simultaneously reduced wear volume, minimized dilution rate and enhanced micro-hardness.

Resumo em Inglês:

ABSTRACT Topology optimization (TO) is a mathematical method that optimizes a part’s layout, maintaining the project’s spatial constraints, considering loads, boundary conditions, and manufacturing to maximize its performance. Through mesh analysis, non-essential areas in the structure are identified, allowing efficient material removal without compromising its integrity. However, it is not usual to use TO without changing the part layout, focusing only on removing its internal mass, as is done in this paper. Therefore, two sets of cylindrical ABS samples were generated: one with an internal structure obtained by TO, varying the density of finite element mesh through the SolidWorks Software, and another with an internal structure chosen in the slicing stage before 3D printing. Then, the samples were subjected to the same compression tests. According to the results, all models support loads above the 10 kN specified. Unlike theoretical expectations, the best performance was from the coarse mesh TO, which was statistically equivalent to the tri-hexagonal and grid infill patterns. However, TOs made with medium and fine mesh pushed the limit of the piece shape, making the wall very thin and reducing its resistance. Using the infill pattern proved to be simpler to execute and less time-consuming to manufacture.

Resumo em Inglês:

ABSTRACT The clamping method of flowmeters in natural gas pipe has a significant impact on improving the calibrated speed and operational efficiency. In this study, a finite element model of the automatic flowmeter clamping device is established, which includes flowmeter, flange plate, screw nut, and DN300 pipe. The stress distribution and variation of the device are investigated for the effects of different external clamping forces and different natural gas pressures. The results indicate that the flowmeter clamping device designed can achieve effective clamping of the flowmeter. Moreover, the overall stress levels are below the material’s allowable stress, which indicates that the mechanical structure is reasonable. In the flowmeter clamping device, the high-stress areas are concentrated on the surface of the flowmeter and the arcuate region at the base of flange plate. When the external clamping force increases from 8 MPa to 12 MPa, the maximum stress of the flowmeter increases by 30 MPa, meanwhile the maximum stress on the flange plate increases only by 15 MPa. When the natural gas pressure increases from 4 MPa to 12 MPa, the maximum stress in the pipe cross-section rises from 25 MPa to 82 MPa.

Resumo em Inglês:

ABSTRACT This study presents the synthesis and characterization of three-dimensional graphene-TiO2 (GT) composites with varying TiO2 content via a hydrothermal method. The composites exhibited a hierarchical porous structure with specific surface areas up to 243.9 m2/g, significantly higher than pure TiO2 (52.3 m2/g). FTIR analysis revealed Ti-O-C bonding, indicating strong interfacial interactions. The composites demonstrated enhanced mechanical properties, with GT-3 showing a compressive strength of 1.15 MPa and an elastic modulus of 11.3 MPa. Photocatalytic experiments showed that GT-3 degraded 92% of methylene blue under UV light in 120 minutes and 67% under visible light in 180 minutes, outperforming pure TiO2. The improved performance was attributed to efficient charge separation, as evidenced by electrochemical impedance spectroscopy and photoluminescence quenching. The composites exhibited excellent reusability, maintaining 94% activity after five cycles. UV-vis diffuse reflectance spectra revealed a narrowing of the band gap from 3.2 eV for TiO2 to 2.5 eV for GT-3, explaining the enhanced visible light activity. These results demonstrate the potential of GT composites for environmental remediation applications.

Resumo em Inglês:

ABSTRACT This research emphasizes the critical role of fire resistance in building structures, with a particular focus on concrete columns, which are vital for maintaining structural integrity during fires. Concrete Encased Steel (CES) columns, featuring steel sections encased in concrete, provide improved ductility, shear strength, and compressive capacity. While the fire-resistant properties of Concrete Filled Steel Tubular (CFST) columns have been widely studied, CES columns are increasingly recognized for their unique advantages. A key research gap exists in predicting the ultimate load of Steel Fiber Reinforced CES columns under elevated temperatures. This study addresses the gap by developing a computational model using Machine Learning (ML) techniques. Forty CES columns, subjected to various conditions such as different concrete types, temperatures, and encasement were experimentally tested. The data was used to train ML algorithms, including Linear Regression (LR), Extreme Gradient Boosting (XGB), Gradient Boost Regressor (GBR), and Voting Regressor (VR), to predict the ultimate load under high temperatures. The model's performance was assessed using R2, RMSE, MSE, and MAE metrics, with XGB outperforming other models by achieving an R2 value of 0.94, indicating excellent predictive accuracy.

Resumo em Inglês:

ABSTRACT In the current study, polypropylene and steel hybrid fiber reinforced self-compacting concrete was analyzed with and without the introduction of carbon nanotubes. A range of workability and hardened properties studies was performed along with the adsorption characteristics. Three different weight fractions including 15, 20, 25 kg/m3 for polypropylene fiber and 3,6,9 kg/m3 of steel fibres were individually and combinedly added. Also, with a fixed volume of 0.4% of carbon nanotubes, the behaviour of SCC was analyzed. To evaluate the fresh properties of Hybrid Fiber Reinforced Self-Compacting Concrete (HFRSCC), V-Funnel, slump-flow and L-box tests were performed. Result reveals that steel fiber and hybrid fiber added self-compacting concrete provides enhanced hardened properties than the polypropylene fiber SCC. Also, the result revealed that with the CNT incorporation, the hardened strength properties were enhanced and however the workability characteristics diminished.

Resumo em Inglês:

ABSTRACT This study explores the complex world of mechanical properties displayed by composites reinforced with natural fibers, concentrating on the features of sisal and abaca fibers in particular. This research aims to thoroughly assess the inherent capabilities of these eco-friendly and renewable fibers as strong reinforcing agents in composite materials. The creation of composite samples with carefully adjusted fiber content and matrix compositions is all part of the study technique. A full investigation occurs, diving into essential mechanical qualities such as compression strength, tensile strength, flexural strength, impact resistance, and water absorption. The impact of relative fiber, and the composites were created by blending sisal and abaca fibers in a range of volume fraction ratios (0.0–1.0, 0.25–0.75, 0.50–0.50, 0.75–0.25, and 1.0–0.0). These trials yield data that are carefully examined in order to decipher the complex interactions among fiber type, and overall mechanical performance. The study incorporates advanced microstructural analysis methods, such as scanning electron microscopy (SEM), to reveal subtleties in the complex interfacial bonding dynamics between the natural fibers and the matrix. This research, which goes beyond the usual limitations, illuminates prospective uses for sisal and abaca natural fibers in composite materials while also enhancing our understanding of the mechanical properties.