Mestrado em Engenharia Mecânica
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- ItemAvaliação da usinabilidade de aços de livre corte com adições de chumbo e/ou bismuto(Universidade Federal do Espírito Santo, 2024-10-14) Alves, João Paulo Luiz Grisotto; Barbosa, Patrícia Alves; https://orcid.org/; https://orcid.org/0009-0009-3872-2301; Orlando, Marcos Tadeu D'Azeredo; Machado, Álisson Rocha; Salustre, Mariane Gonçalves de MirandaFree-cutting steels are developed using metallurgical techniques to achieve high machinability through the addition of alloying elements that disrupt the material matrix, enhancing productivity and reducing manufacturing costs. This study aimed to evaluate the machinability of the three free-cutting steels, coded as Steel A (MnS+Pb), Steel B (MnS+PbBi), and Steel C (MnS+Bi). For this purpose, microstructural characterization, hardness tests, and machining tests were conducted, including constant pressure drilling tests (evaluating drilled length, cutting temperature, and chip characteristics) and turning tests (measuring machining force, specific cutting pressure, surface roughness parameters, chip characteristics, and tool wear). In the drilling tests, spindle speed, applied load, and material were varied. In the turning tests feed rate and material were varied. The results indicated that Steel A exhibited a predominantly pearlitic microstructure, while Steels B and C showed ferritic microstructures. These microstructural differences were reflected in the Vickers hardness values, with Steel A showing a hardness 78% and 84% higher than that of steels B and C, respectively. In drilling process, Steel A presented greater machining difficulty, with Steels B and C being the materials with the best machinability responses. Increasing spindle speed or applied load resulted in a higher material removal rate. Lower spindle speed combined with greater applied load resulted in higher temperatures during drilling of free-cutting steels. Increasing applied load contributed to the breakage of the chip, forming shorter chips. Lead and bismuth additions contributed to chip embrittlement, however, only bismuth addition showed tendency to longer and snarled chips formation. In turning process, different microstructures, free cutting elements and hardness promoted changes in the material machinability. At lowest feed rate, FU for Steel C was 105% higher than the others. For f=0.2 mm/rev, FU for Steel A became the superior. And for the greatest feed rate, Steel A showed the better machinability result, presenting a FU value 15.2% lower than Steels B and C. The specific cutting pressure (Ks) showed significant variations depending on the feed rate and materials. Free cutting elements contributed to Ks reduction. The free cutting steels showed similar behavior, increasing roughness with feed rate. Material and feed rate influenced the chip shape during the turning process. In general, chip breaking was facilitated by feed rate increasing. Bi addition contributed to chip embrittlement, making it shorter. Cutting tool used for turning Steel A showed the greatest wear (VBBmáx = 844.523 µm, and crater), the largest build up layer, and evidence of wear mechanisms by diffusion and attrition
- ItemAvaliação da performance de medição de gás úmido pela tecnologia de cone invertido por ciência de dados(Universidade Federal do Espírito Santo, 2024-10-30) Lima, Phelipe Augusto Santos Oliveira; Ramos, Rogério; https://orcid.org/0000-0003-4493-2435; Martins, Marcio Ferreira; Tsuzuki, Marcos de Sales GuerraA particular case of multiphase Cows is that of wet gas, which is present in various industrial sectors such as power generation, the food industry, chemicals, and primarily in the oil and gas industry. Monitoring this Ćow is of utmost importance to meet not only legal requirements but also production outlook and the design and development of new techniques to enhance well efficiency. It is known that the presence of water at high Gas Volume Fractions, in other words, in wet gas conditions, leads to an overreading tendency in measurements by differential pressure meters. Therefore, being a low-cost technology with a well-known physical principle, the use of these meters for wet gas applications is gaining prominence in the industry. Inverted cone meters are the most recent technology in differential pressure Ćow measurement, standing out for their low pressure drop and the requirement for shorter straight pipe lengths when compared to oriĄce plates. Therefore, considering the applicability of statistical inference techniques and the data processing capabilities of data science for multidimensional data, the implementation of various techniques becomes one of the possible tools for assessing the performance of two-phase Ćows. The experimental results obtained indicate a linear relationship between overreading, pressure, and the dimensionless Lockhart-Martinelli parameter. The methodology of this work aims to contribute to the implementation of new techniques for correcting overreading in two phase Ćows.
- ItemAvaliação microestrutural de cordão soldado a laser Utilizando mistura metal-cerâmica (uns s32304-tib2)(Universidade Federal do Espírito Santo, 2024-10-14) Xavier, Gabriel Correa; Orlando, Marcos Tadeu DAzeredo; https://orcid.org/0000-0002-8387-6504; Passos, Carlos Augusto Cardoso; Rossi, Jesualdo Luiz; Passamai Junior, José Luis; Salustre, Mariane Gonçalves de MirandaDuplex stainless steels (DSS) are widely used due to their good corrosion resistance and high mechanical strength, when compared to austenitic stainless steels, especially in corrosive environments such as nuclear, chemical, petrochemical, and offshore oil and gas industries. This class of materials requires careful control of cooling rates during welding, both to maintain the appropriate ferrite-austenite ratio and to prevent the formation of detrimental precipitates. The high concentrated energy released during laser welding is advantageous in producing limited heat-affected zones and high cooling rates, which hinder the formation of undesirable precipitates. With the aim of combining the good mechanical characteristics found in DSS with low density and high process yield found in ceramic compounds, there is a strong industry trend towards producing powder metallurgy sintered stainless steel composites. Therefore, the objective of this dissertation is to evaluate the properties of laser-welded joints in UNS S32304 duplex stainless-steel sheets using a mixture of the same steel powder with varying proportions of titanium diboride ceramic. Several techniques, such as X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), microindentation, and microtomography were employed to characterize the microstructure and hardness of the samples welded with the manufactured powder. The results revealed a deviation from the ideal ferrite-austenite ratio in welded joints when TiB2 ceramic was introduced, primarily attributed to the formation of titanium nitride (TiN). Microhardness tests indicated an increase in hardness in the fusion zone as a function of TiB2 content in the samples and due to the presence of the formed titanium nitride. Furthermore, microtomography revealed improved weld bead homogeneity and a narrower fusion zone in samples containing TiB2, suggesting enhanced weld quality. These findings highlight the potential of TiB2 ceramic as an effective reinforcement in improving the microstructural and mechanical properties of laser-welded DSS joints, promising advancements in the manufacturing of corrosion-resistant materials for various industrial applications.
- ItemEstudo do comportamento em desgaste microabrasivo da liga Nb-Ni-WC-Cu sinterizada a plasma pulsado(Universidade Federal do Espírito Santo, 2024-11-11) Souza, Juliana Prates; Bozzi, Antônio Cesar ; https://orcid.org/0000-0003-4857-0216; http://lattes.cnpq.br/3017292130810807; https://orcid.org/0009-0001-4353-5991; http://lattes.cnpq.br/7583082369760297; Orlando, Marcos Tadeu D´Azeredo ; https://orcid.org/0000-0002-8387-6504; http://lattes.cnpq.br/3562894103432242; Franco Júnior, Adonias Ribeiro ; https://orcid.org/0000-0003-0511-1052; http://lattes.cnpq.br/6677652514776940There is an increasing demand in the industry for alloys with increasingly enhanced mechanical properties. Aiming at high-temperature applications, the Nb-Ni-WC-Cu alloy was developed in a previous study by spark plasma sintering (SPS) in three different nickel compositions (5%, 10%, and 15%) and sintered at three distinct temperatures (1000°C, 1100°C, and 1200°C). The objective of this work was to investigate the micro-abrasive wear behavior of this alloy. For this, Vickers hardness tests and micro-abrasion tests were carried out using three abrasives: alumina (Al₂O₃), silicon carbide (SiC), and silica (SiO₂). The results indicated that increasing the sintering temperature led to an increase in the hardness of the samples. The composition with 10% nickel sintered at 1100°C (M2 1100) showed the highest hardness (1345.80 HV). The micro-abrasion test was conducted in a fixed-ball configuration, with a load of 0.3 N and a rotation speed of 20 rpm, using an abrasive suspension with a concentration of 0.1 g/cm³ for Al₂O₃ and SiC, and 0.35 g/cm³ for SiO₂. The best results regarding abrasive wear were obtained for the samples sintered at 1100°C, for all compositions. Through scanning electron microscopy (SEM), it was observed that the predominant wear mechanism was grooving for the Al₂O₃ and SiO₂ abrasives, and rolling and mixed mechanisms for the SiC abrasive
- ItemInterfaces e estratégias de controle baseadas em machine learning aplicadas a um exoesqueleto de braço para reabilitação motora(Universidade Federal do Espírito Santo, 2024-09-17) Dias, Eduardo Antonio Fragoso; Andrade, Rafhael Milanezi de; https://orcid.org/0000-0002-2839-3649; Bastos Filho, Teodiano Freire; Vimieiro, Claysson Bruno SantosStroke is one of the leading causes of acquired disability worldwide, with approximately 80% of survivors living with permanent disabilities. Recovery of upper limb functionality is particularly challenging, with only about 50% of patients regaining some functional use after the event. In this context, physiotherapy and occupational therapy are essential, but robotic rehabilitation emerges as a promising alternative to enhance therapeutic outcomes. However, the effectiveness of these new therapies is directly linked to the control interfaces and strategies applied in the patient’s interaction with the robotic device. Thus, this work investigates the development and application of control strategies and interfaces in an arm exoskeleton designed for neuromotor rehabilitation of post-stroke patients. We explore different strategies using surface electromyography (sEMG) to identify the patient’s movement intention and strategies operated by the physiotherapist, applied to an upper limb exoskeleton. Additionally, a rehabilitation protocol was implemented using an interface based on assistive trajectory control. The results indicate significant improvements in rehabilitation, highlighting the efficacy of incorporating advanced robotic technologies in the neuromotor recovery process, providing a more effective and individually tailored approach to patient needs.