Resumo em Inglês:

Abstract Soft landfilling is still a major challenge for geotechnical engineering, including road engineering. These soils present great constructive difficulties because of their peculiar characteristics, such as low carrying capacity and high compressibility. Several techniques have been adopted in landfill foundations on soft soils to accelerate and stabilize the settlements, and each one has advantages and disadvantages on its use, depending on the analyzed case. This article presents a case study of a soft soil landfill foundation along highway BR-381 (Fernão Dias) – North Road. The place under study is 120 meters long and had a settlement in the road caused by the presence of compressible soil in its subgrade. To solve the problem, the settlements versus time were analyzed in four geotechnical solutions. After carrying out the analyses and computational studies for proposed solutions, it was concluded that only two of them could be performed for the case studied, mainly, the use of deep drainage of the foundation on the landfill or application of temporary overweight.

Resumo em Inglês:

Abstract One of the methods to minimize the negative impact caused by inadequate disposal of Water Treatment Plant Sludge (WTPS) is to mix it with the soil, applying the material in engineering works. In this research, the objective was the use of WTPS for soil stabilization purposes, verifying the improvement of the characteristics and properties with 0%, 15%, 30% and 50% of sludge, for application in the base and sub-base layers of road pavements. Characterization, compaction, permeability, Resistance to Simple Compression (RCS), and California Bearing Ratio (CBR) tests were carried out. However, none of the mixes met all the necessary requirements for use in the pavement layers, but it is concluded that there was an increase in the RCS, CBR and impermeability of the mixtures compared to the reference mixture (100% soil). The RCS increased 142.75% of the soil for a blend with 30% sludge, CBR increased 76.52% of the soil for mixture with 50% WTPS, and the permeability of blends with 15%, 30% and 50% sludge was lower than then with only the soil. These results show that these mixtures can be useful for other types of applications in Geotechnics, being able to contribute to the sustainable destination of WTPS.

Resumo em Inglês:

Abstract In this research, the coupled fluid-structure forced vibrations (harmonic load) of the Koyna gravity dam are studied. Using the finite element method (FEM), the influence of structural damping and fluid compressibility are studied for different reservoir dimensions of the dam. The numerical approach is done through the U-P formulation (structure displacement and pressure for fluid). Thus, the spectral response of structural displacements and of hydrodynamic pressures were investigated with different structural damping rates, both considering incompressible and compressible fluids. With analyses, the greater the effect of the structure's damping, the lower the displacement and the hydrodynamic pressure amplitudes. The structural damping has the same effect tendency in both incompressible and compressible fluids. Furthermore, for the incompressible fluid, the coupled modes are not infuenced by the length of the reservoir, there are no acoustic modes identifed and the mass modes are predominantly identifed. With the compressible fluid, the analysis of the dominant modes showed that the fundamental mode is not altered by the length of the reservoir, but from the second mode onwards, each cavity geometry predominates in the vibration, and it is necessary to evaluate the frequency range of the structure and the fluid separately. Therefore, the harmonic numerical analysis of the present study contributes with innovative results of the Koyna dam and in the analysis of the effects involved in Fluid-Structure Interaction (FSI) simulations of other problems related to Dam-Reservoir Interaction (DRI).

Resumo em Inglês:

Abstract Lateral-Torsional Buckling (LTB) is an important limit state that must be considered in the design of steel members subjected to bending. During the process of revising of the Brazilian Standard ABNT NBR 8800:2008, it was questioned whether the present formulation would really lead to good results vis-à-vis the experimental tests. To this end, a comprehensive review of the technical literature was carried out, looking for test results that could be compared with the ones using the equations provided in the Brazilian Standard. Then, a meta-analysis was performed by comparing the test results with the ones of the ABNT NBR 8800:2008 methodology. It was observed that, for beams subjected to uniform bending moments and simple supports, the formulation proved to be adequate. However, for the case of beams with variable bending moments, for which the factor Cb (modification factor for non-uniform bending moment diagram) is used, it was realized that the formulation could lead to unsafe results, especially for high values of Cb. A modified formulation was then proposed, with the introduction of Cb only in the elastic range of the equations (only in the buckling moment equation) and in the equation for the slenderness parameter corresponding to the beginning of yielding, λΓ. The proposed modified formulation, as well as the EN 1993-1-1:2022 methodology, were subsequently included in the meta-analysis. Structural reliability analyses were also carried out for both the ABNT NBR 8800:2008 and the modified methodologies. The analyses showed that the reliability indexes of the modified formulation were higher than those of the ABNT NBR 8800:2008 one and closer to the recommended "target value".

Resumo em Inglês:

Abstract The occurrence of fires can lead to accidents with high potential, and vertical fire compartmentation is a measure to reduce these incidents. Increasingly, computational numerical analyses play a crucial role in studying fire behavior for control and mitigation. The computational tool Fire Dynamics Simulator (FDS) is one of the main programs aimed at numerically analyzing fire spread. By using the FDS program, this research aims to numerically analyze the effectiveness of using horizontal projection and the combination of horizontal and vertical projections simultaneously, as specified in the Technical Instruction of the Fire Department of the State of São Paulo in combating the propagation of external vertical fire to the facade. Temperature measurements on the compartment facade were used to compare temperatures on the upper floor with the autoignition of material values commonly found in facades. Models with only horizontal projections showed greater effectiveness compared to models with the combinations of projections, mainly due to the presence of the spandrel component, which has a harmful effect on fire propagation. Despite the lower effectiveness of combination models for a fire with a heat release rate of 300 MJ/m², there would be no external vertical fire propagation.

Resumo em Inglês:

Abstract The main coal reserves in Brazil are located in the southern region, where the most important coalfield, including the Candiota mine, is found. The mineral exploration and mine planning programs of the companies mining these coal deposits are generally restricted to drilling data and cores, despite the exploratory potential of geophysical methods in coal prospecting. This study aims to investigate the ability of the seismic method known as Multichannel Analysis of Surface Waves (MASW) to identify coal seams in the Candiota area. The MASW method allows obtaining a layer model composed of a low-velocity (blind) layer and/or relatively thin (hidden) layer from the surface wave dispersion curves. The hidden and blind layer problems are pitfalls of the traditional seismic refraction method and the geological settings related to coal seams may encompass both problems. In addition, the Candiota mine has conditions favorable for applying the MASW method due to the shallow depths of the coal seams. The study was based on the analysis of synthetic seismic data generated from a 3-layer conceptual model of the Candiota deposit. The dispersion curves of the fundamental mode of the Rayleigh surface waves were generated and the effects of each of the parameters of the seismic model were evaluated, as well as the relationship between the parameters through objective function tests. A new inversion algorithm capable of obtaining the true model was implemented. The results obtained from the application of the inversion algorithm demonstrated the potential of the MASW method in identifying coal seams from S-wave profiles and proves it to be a powerful tool for coal mineral exploration programs.

Resumo em Inglês:

Abstract The metalworking industry faces challenges in maintaining process performance due to variables affecting product quality, particularly in processes requiring precise control over machined part finishes. Duplex stainless steels, known for their high strength, work hardening, and low thermal conductivity, pose specific machining challenges that can hinder producing high-quality components and equipment. This study aimed to determine optimal parameters for end milling of duplex stainless steel UNS S32205. Formulated as a combined objective function derived from minimizing the mean square error (MSE) for parameters Ra and ßf, subject to a common constraint. The optimization was conducted using generalized reduced gradient (GRG). A Pareto frontier was constructed, offering efficient results with Ra = 0.4534 μιη and Rt = 3.2671 μιη for varying weights assigned to Ra and Rt. Adjusting weights in the objective function allowed prioritization based on specific needs. Optimal input parameters were identified as cutting speed (vc) = 60.79 m/min, feed per tooth (fz = 0.15 mm/tooth, axial depth of cut (ap) = 0.90 mm, and radial depth of cut (ae) = 16.31 mm, simultaneously optimizing both parameters. This approach reduced the mean square error (RMSE), determining roughness Ra and Rt mean and variance, thus improving the machining process. Confirmatory trials using an orthogonal Taguchi arrangement (L9) yielded results within the algorithm's confidence interval. This research offers a robust methodology for optimizing machining parameters, enhancing product quality in the metalworking industry.

Resumo em Inglês:

Abstract The purpose of this study was to evaluate the cleanliness of Interstitial Free (IF) steels produced in a Ruhrstahl Heraeus (RH) vacuum degasser by determining the level of Al2O3 and Al-Ti-O inclusion types generated in three different process conditions: i) steel processed without thermal intervention; ii) steel processed with chemical heating and iii) steel processed with cooling by the scrap addition. The inclusion formation and remotion during these processes were analyzed. The influence of homogenization time was also studied. The content of inclusions was measured by a Scanning Electron Microscope (SEM) with an automated counting system denoted as Automated Steel Cleanliness Analysis Tool (ASCAT). This method can provide the size and composition of non-metallic compounds. The results have shown that the Ruhrstahl Heraeus (RH) process can improve the remotion efficiency of the inclusions, such as those larger than 2.5 mm, which is due to the molten steel circulating in RH vessel. For some inclusion types, higher concentrations were detected, but their size was smaller. For a heat where it was necessary to apply chemical heating using Al addition and O injection, there was detected a higher concentration of inclusions when compared with that cooled by scrap addition. In cooling heats, there is a strong generation of small and thin inclusions (<1.0 mm) that are very difficult to be removed from liquid steel. The size of the Al2O3(s) type is around eight times larger than Al-Ti type inclusions.

Resumo em Inglês:

Abstract The aim of this study was to verify the pitting corrosion behavior in the surface layers obtained by plasma nitrocarburizing at 400 and 450 °C/5 h on two types of super-martensitic stainless steel, namely micro-alloyed (Nb-SMSS) and unalloyed (SMSS). The results reveal that in all the nitrocarburized layers, a discontinuous, thin layer measuring less than 5µm in thickness exhibits a microhardness exceeding 950 HV0.05, for the two steels. Furthermore, the structure of the surface layer is a combination of expanded austenite (γN), expanded martensite (α`N), ε-Fe2-3N, cementite (θ-Fe3C), and traces of CrN. The surfaces exhibit poor corrosion resistance across all layers, which can be attributed to localized micro-galvanic corrosion between the iron nitride (ε-Fe2-3N) and expanded austenite (γN), since they are known to have higher corrosion resistance, as well as expanded martensite ((α`N) and cementite (θ-Fe3C), which have lower corrosion resistance. This corrosion process initiates after the dissolution of the surface layer in a 3.5% NaCl solution, subsequently leading to substrate corrosion.

Resumo em Inglês:

Abstract A Hollow Cathode Plasma Enhanced Chemical Vapor Deposition (HC-PECVD) reactor was used to deposit silver doped Diamond-Like Carbon (Ag-DLC) films on Ti6Al4V alloy employing two methodologies: i) producing a silicon interlayer, using tetramethylsilane (TMS) as silicon precursor, varying the argon flow of the hollow cathode; and ii) carbonitriding the substrate. Profilometry, Raman, and Secondary Ion Mass Spectrometry (SIMS), as well as nanohardness, micro-scratch, scratch, and VDI 3198 indentation tests were used to evaluate the characteristics of the films and their adhesion on the substrates. The results demonstrated that the argon flow can be used for tuning the Ag-DLC film’s hardness, toughness, and adherence on silicon interlayers. The carbonitriding process, in turn, provided an improvement in the film toughness compared with non-carbonitrided samples. Considering the lower cost and easier handling of N2 compared to the silicon precursors commonly available (TMS, HDMSO, SiH4, etc.), the carbonitriding process proved more appropriate to improve the adhesion of the Ag-DLC films on the Ti6Al4V alloy.

Resumo em Inglês:

Abstract This article analyzes the operational variables of a catalytic cracking plant that affect the catalytic circulation and conversion results. It is considered that the analysis of the impact of these variables on the catalytic circulation is essential for the refiner to determine the best operational strategies, without loss of profitability and to minimize friction mechanisms, which reduce particulate emissions. The Analysis of Variance revealed how, statistically, the parameters are related, presenting equal, opposite directions and with different magnitudes. The results of R2, F significances and analysis of residuals showed an excellent fit of the model, therefore, validating the design of the experiments carried out. The application model demonstrated a reduction capacity of 25% in the circulation of the catalyst, with no impact on the conversion of the unit. This result demonstrates the refiner's ability to act, improving its unit optimization techniques from an environmental and economic bias.

Resumo em Inglês:

Abstract The Oil and Gas (O&G) sector is facing unprecedented challenges regarding greenhouse gas (GHG) emissions, urging rapid decarbonization actions in line with global imperatives. This comprehensive review article delves into the crucial role of industry standards in spearheading transformative efforts. It synthesizes findings from a literature review, offering insights into real-world implementation cases within the O&G industry, and integrates perspectives from specialists through qualitative research. Key standards from the International Organization for Standardization (ISO), notably TC 301 and ISO 50001, are highlighted for their pivotal role in promoting energy management systems as essential tools for GHG mitigation. These standards not only advocate for energy-saving practices but also emphasize structured energy management to effectively reduce greenhouse gas (GHG) emissions. Additionally, the influential ISO/TC 67 orchestrates a comprehensive suite of standards tailored for the O&G industry, facilitating its adaptation to evolving technological and environmental landscapes. Complementary collaborative initiatives such as IPIECA, OGCI, and IOGP emerge as vital forces in promoting operational and strategic solutions. Through this review study, the intertwined relationship between energy management and GHG emission reductions is elucidated, underscoring how industry standards and collective efforts can drive the O&G sector towards a more sustainable future in alignment with global environmental ambitions.