Mestrado em Engenharia Mecânica

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Agora exibindo 1 - 5 de 294

Avaliação da tensão residual em componentes manufaturados com MADA usando a técnica de ruído magnético de Barkhausen
(Universidade Federal do Espírito Santo, 2026-02-12) Fundão, Felipe Soares; Liskevych, Olga; https://orcid.org/0009-0003-5739-0433; http://lattes.cnpq.br/0753194047704597; Macêdo, Marcelo Camargo Severo de; https://orcid.org/0000-0002-2206-6081; http://lattes.cnpq.br/5530638975120211; https://orcid.org/0009-0006-6221-4196; http://lattes.cnpq.br/7385765276852063; Pardal, Juan Manuel; https://orcid.org/0000-0001-9625-4547; http://lattes.cnpq.br/3583921436364162; Tavares, Sérgio Souto Maior; https://orcid.org/0000-0003-3606-9272; http://lattes.cnpq.br/4320367144812616
Additive manufacturing (AM) has emerged as an efficient alternative to traditional manufacturing methods, enabling the production of complex parts with reduced material waste. Among the available processes, Wire Arc Additive Manufacturing (WAAM), a type of Directed Energy Deposition (DED), uses a welding arc as an energy source and a metallic wire as feedstock. However, intense thermal cycles and rapid solidification can generate significant residual stresses, compromising the structural integrity of the components. This study investigated residual stresses in WAAM produced parts using a 1.2 mm ER70S-6 wire on an AISI 1020 substrate through Magnetic Barkhausen Noise (MBN). This magnetic technique is sensitive to induced stresses and allows for fast measurements without special sample preparation. The analysis focused on two main parameters: voltage and frequency. The results demonstrated that frequency directly influences the penetration depth of the magnetic field and the intensity of the Barkhausen effect, affecting the MBN response. Higher frequencies reduced penetration depth and increased the root mean square (RMS) values of the signal. Residual stress distribution maps were compared with finite element simulations and hole-drilling measurements from previous studies, showing good correlation. These findings confirm the feasibility of MBN as a quality control tool for DED-manufactured components, provided that test parameters and possible microstructural transformations are carefully considered.
Fabricação, caracterização e avaliação de desempenho em usinagem de metal duro com adição de grafeno sinterizado por plasma pulsado
(Universidade Federal do Espírito Santo, 2025-09-30) Rosa, Jhonatan Dantas dos Santos; Carneiro, Marcelo Bertolete; https://orcid.org/0000-0001-5817-8475; https://lattes.cnpq.br/5985238373861974; Barbosa, Patrícia Alves; https://orcid.org/0000-0003-1930-0815; https://lattes.cnpq.br/8803458151203934; https://orcid.org/0009-0003-5871-7434; https://lattes.cnpq.br/2127527753095331; Machado, Izabel Fernanda; https://orcid.org/0000-0002-1079-0777; https://lattes.cnpq.br/6705415923436933; Filgueira, Marcello; https://orcid.org/0000-0001-5297-0250; https://lattes.cnpq.br/0725750287341168
Cemented carbide, primarily composed of tungsten carbide (WC) and cobalt (Co), is the most widely used cutting tool material in the metalworking industry. Even with its excellent hardness and toughness properties, cemented carbide continues to be the focus of constant development, such as the addition of graphene. This nanoadditive promises to increase the performance of conventional materials by improving mechanical and lubrication properties. In this regard, this work aims to fabricate, characterise and evaluate the machining performance of cemented carbide with fewlayer graphene (FLG) addition. For this purpose, WC-10Co+0.1FLG and WC-10Co samples were sintered by spark plasma (SPS) at 1400°C, with uniaxial pressure of 40MPa in vacuum. Some of these samples were used for microstructural, hardness, fracture toughness, and density characterisation. Others were ground to produce cutting tools. The SPS-sintered tools with and without graphene addition were compared with a commercial insert (WC-Co - Commercial). Dry turning tests on grey cast iron FC250 were carried out under constant cutting conditions (Vc=150 m/min, f=0.15 mm/rev and ap=1.5 mm). Machining force, apparent coefficient of friction, cutting temperature, surface roughness parameter and tool wear were evaluated. The results showed that the addition of 0.1%wt of FLG has little influence on densification, with no effect on hardness; however, it promoted an average increase of 13.82% in fracture toughness. Graphene addition also promoted a overall gain in cutting tool performance, significantly reducing the machining force, the apparent coefficient of friction, and cutting temperature by 40.17%, 46.13% and 15.65%, respectively, compared to commercial insert. Furthermore, the nanoadditive improving the surface finish, reducing Ra by 68.75% compared to the commercial cutting tool. Regarding SPS-sintered tools, the graphene contributed to a 19.56% reduction in FU and a 29.22% reduction in the apparent friction coefficient. The WC10Co+0.1FLG tool showed crater wear (KB) of 448 µm and flank wear (VBB) of 218.3 µm. The last one was approximately three times smaller than the other inserts evaluated, with attrition as the dominant mechanism. Therefore, 0.1%wt of few-layer graphene (<10) added to cemented carbide (WC-10Co), which provides self lubrication and increased thermal conductivity, as well as fracture toughness; together with SPS sintering technique, which promotes high physical-mechanical characteristics; are shown as promising, innovative and efficient alternatives in the machining process sustainability.
Mecanismo antitravamento para redutores harmônicos : aplicação em atuadores de próteses ativas de membro inferior
(Universidade Federal do Espírito Santo, 2026-01-30) Fiorezi, Guilherme Gomes; Andrade, Rafhael Milanezi de; https://orcid.org/0000-0002-2839-3649; http://lattes.cnpq.br/9241045307171389; https://orcid.org/0000-0003-1964-3957; http://lattes.cnpq.br/6210607874686902; Loeffler Neto, Carlos Friedrich; https://orcid.org/0000-0002-5754-6368; http://lattes.cnpq.br/3102733972897061; Siqueira, Adriano Almeida Gonçalves; https://orcid.org/0000-0003-0663-156X; http://lattes.cnpq.br/2935052598064187
Actuators are essential for the operation of a wide range of robotic systems across various modern industries. These actuators are usually equipped with gear reducers directly coupled to the motors and, depending on their type, may be more or less affected by overload events. Harmonic drives, despite their many advantages, are among the most susceptible to overloads and may, in many cases, experience the so-called ratcheting phenomenon. In such events, the actuator may lock and potentially lead to reducer failure. For this reason, torque limiters are widely employed in industrial systems; however, commercial torque limiters typically fully decouple the actuator from the output when activated. As a result, in addition to their excessive size, these devices do not address issues that may arise during their actuation in medical devices, such as prostheses, where complete decoupling can lead to user falls due to loss of controllability. In this context, this work presents a design methodology for an anti-lock mechanism that maintains partial coupling between the actuator motor and the output through springs, providing passive overload absorption and compliant behavior. The proposed methodology addresses the calculation of the desired maximum torque and the torsional stiffness after mechanism actuation. For practical application and demonstration, a mechanism is designed for the ankle joint of the UFES Robotic Leg prosthesis. The anti-lock mechanism is tested on a bench setup to verify the theoretically obtained values and with a human subject performing four activities of daily living to validate the concept and evaluate the impacts of incorporating the mechanism. Overall, the results indicate that the designed mechanism, using the proposed methodology, meets the established design requirements, allowing movements to be performed in a manner very similar to that observed prior to its installation on the prosthesis. The prototype weighs 229 g, has an average torque limit of 60.91 Nm, an average torsion stiffness of 241 Nm/rad, and about ±10° of angular displacement. Some results require manufacturing the parts again to confirm the true origin of the discrepancies; however, other minor differences between the modeling and experimental results can be reduced through improvements in the modeling, such as the inclusion of the effects of torsional springs after a better understanding of their influence.
Desenvolvimento e aplicação de metodologias de ciência de dados para análise de performance de medidores de vazão multifásicos por dados de vaso separador
(Universidade Federal do Espírito Santo, 2025-12-19) Lacourt, Gustavo Grecco; Ramos, Rogério; https://orcid.org/0000-0003-4493-2435; http://lattes.cnpq.br/2975022316691139; Santos, Guilherme Fabiano Mendonça dos; https://orcid.org/0000-0001-8660-8671; http://lattes.cnpq.br/4995407690243279; https://orcid.org/0009-0006-2040-926X; http://lattes.cnpq.br/3010953674590903; Martins, Ramon Silva; https://orcid.org/0000-0002-4905-1453; http://lattes.cnpq.br/0642654456195324; Morellato, Saulo Almeida; https://orcid.org/0000-0002-8861-9873; http://lattes.cnpq.br/0656426665090126
The oil industry is characterized by multiphase flows typically involving oil, gas, and water, which are separated on production platforms by separator vessels, enabling the individual measurement of each phase’s flow rate. Due to the size, weight, and cost of these vessels, there is increasing interest in the use of multiphase flow meters (MPFMs) as alternatives for field testing. This dissertation applies a calibration and validation methodology for MPFMs based on reference data obtained from single phase meters positioned downstream of separator vessels. The methodology combines calibration factors with time-series analysis techniques, including stationarity tests (ADF and KPSS), autocorrelation (ACF) and partial autocorrelation (PACF) functions, and cross-correlation (CCF). These tools enable the investigation of temporal coherence between signals and the identification of physical delays arising from the layout of the instruments in the plant. Data from 27 tests conducted in two campaigns, covering seven wells on a Brazilian offshore platform, were analyzed. The results showed that while MPFMs estimate total liquid flow with good accuracy, significant deviations occur in the measurement of individual phases, particularly oil. Calibration factors substantially reduced these deviations, as confirmed by the Mean Absolute Percentage Deviation (MAPD), which indicated average reductions from 58.36% to 8.74% for oil, from 10.46% to 1.69% for water, and from 29.36% to 24.92% for gas. Calibration factors also exhibited temporal stability, remaining valid in subsequent days, and calibration based on only four hours of data produced consistent factors, which is particularly relevant for compliance with resolutions defined by the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP). In addition, the Kruskal–Wallis test demonstrated the need for well-specific calibration rather than calibration solely by device. Cross correlation analysis revealed average physical delays of approximately 86 seconds between the MPFM and the separator, whose consideration contributed to additional improvements in the accuracy of gas measurements.
Dimensionless general transient modeling for smoldering combustion reactors
(Universidade Federal do Espírito Santo, 2025-11-28) Riguetti, Ruan Schultz; Bittencourt, Flávio Lopes Francisco; https://orcid.org/0000-0001-8262-4762; http://lattes.cnpq.br/5146106444604968; Martins, Márcio Ferreira; https://orcid.org/0000-0002-3023-222X; http://lattes.cnpq.br/7325983059020104; https://orcid.org/0009-0006-3930-3238; http://lattes.cnpq.br/9898170192539302; Errera, Marcelo Risso; https://orcid.org/0000-0002-9394-2712; http://lattes.cnpq.br/1262935578021391; Zanoni, Marco Aurélio Bazelatto; https://orcid.org; http://lattes.cnpq.br/8828842714913542; Klippel, Mirian Suely; https://orcid.org/0000-0003-1597-8928; https://lattes.cnpq.br
Smoldering combustion is a slow, flameless process that occurs at relatively low temperatures and reaction rates, typically under limited oxygen conditions. Beyond its scientific interest, this process offers environmental, technological, and social benefits, which make it relevant for both industrial applications and sustainable development. In this context, the present research develops and applies a general dimensionless numerical model for smoldering combustion reactors, aiming to simulate the phenomenon on a small scale. The approach relies on a 2D axisymmetric model implemented in COMSOL Multiphysics (v5.4) using the Local Thermal Non-Equilibrium (LTNE) consideration, which allows separate treatment of the solid and fluid phases. Conservation equations for mass, momentum, energy, and species transport were implemented in a dimensionless form and enable a comprehensive and generalized analysis of the physical and chemical processes involved. Novel dimensional and dimensionless groups emerged during the non-dimensionalization process, associated with the effects of particle-bed burning and the interstitial chemical kinetic dynamics. Classical numbers such as Prandtl, Grashof, Darcy, Schmidt, and Peclet numbers also appeared. The model proposed in the methodology was validated through three case studies. The first involved combustion at the fluid–porous interface, highlighting the influence of natural convection. In this case, the model reproduced the same recirculation patterns reported in the reference study and also allowed vi investigation of how the velocity profile was distorted by these recirculations. The second case addressed the cooling of a porous bed and was used to calibrate convective heat transfer under transient conditions. The results showed that the model is capable of simulating studies without a reactive porous bed, although a maximum discrepancy of 25% was observed in the temperature profiles when comparing the simulations with the experimental data. The third case consisted of a full simulation of smoldering combustion, which included the ignition process through a heat source, propagation of the combustion front, and coupled interactions between heat and mass. This case allows analysis of solid fuel consumption over time and comparison of temperature profiles with experimental data obtained at different axial positions of the reactor. In general, the results demonstrate that the model created is capable of capturing the main behaviors with good agreement compared to the experimental data and the results from the literature. Therefore, the proposed methodology provides a reliable model that allows one to understand smoldering dynamics

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