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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 this work, tungsten oxide (WO3) and different concentrations of transition metal ions doped WO3 (V/Cu:WO3) were prepared by hydrothermal method. X-ray diffraction results confirmed the monoclinic structure of both pristine and doped WO3 nanoparticles (NPs). After doping, the average crystallite size of WO3 decreases from 58 nm to 41 nm for V:WO3 and 42 nm for Cu:WO3 NPs. Field emission scanning electron microscopy analysis confirmed the nanoflake (NF) morphology of all the synthesized NPs. Energy dispersive X-ray analysis and X-ray photoelectron spectroscopy analysis confirmed the presence of V and Cu in the doped NFs. Raman spectral studies provided information about chemical structure and phase crystallinity. UV-visible diffuse reflectance spectroscopy showed that V and Cu doping in WO3 significantly modified their optical properties by extending the absorption spectrum to the visible range and enhancing visible-light absorption. V and Cu doping reduced the bandgap of WO3 from 2.84 eV to 2.57 eV and 2.55 eV respectively. Photoluminescence spectrum showed that the intensity of emission peaks reduced for V:WO3 and Cu:WO3 compared to pristine WO3 NFs. Finally, all these results confirmed that both V:WO3 and Cu:WO3 NFs are suitable candidates for various visible light driven applications including photodetecting and photocatalytic devices.Resumo em Inglês:
ABSTRACT The objective is to develop a composite gel made of graphene and silicone to prevent and extinguish coal seam fires. This is accomplished by integrating the dielectric properties and thermal stability of silicone polymer with graphene. Mechanical mixing and ultrasonication ensure an even distribution of graphene throughout the silicone matrix, yielding a dielectric constant of 18.14 at 1 kHz. The optimal composition includes 3 wt% graphene with a foaming expansion rate of 2. To enhance fire-extinguishing capabilities, sodium silicate gel, a well-known fire suppressant, is incorporated in a 1:1 ratio with silicone polymer. This combination boosts thermal stability and forms a barrier against oxygen infiltration, a key factor in fire prevention. The graphene is prepared through ultrasonic dispersion in ethanol, followed by vacuum drying and blending with silicone polymer and sodium silicate using a planetary mixer. The resulting composite gel exhibits excellent fire-resistant properties, demonstrating its potential in mitigating coal seam fires. Laboratory tests simulating coal seam fire conditions confirm the gel’s effectiveness in reducing temperatures and extinguishing fires. This innovation underscores the potential of graphene-silicone polymer composite gels in advancing fire protection technologies within the mining industry.