Mestrado em Engenharia Mecânica
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- ItemMecanismo 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/2935052598064187Actuators 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.
- ItemDesenvolvimento 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/0656426665090126The 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.
- ItemDimensionless 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.brSmoldering 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
- ItemDesenvolvimento de atuadores flexíveis com elastômeros dielétricos constrito por fibras com sensores de fibra óptica integrados(Universidade Federal do Espírito Santo, 2025-10-09) Silva, Alexandre Bernardo Santos da; Andrade, Rafhael Milanezi de; https://orcid.org/0000-0002-2839-3649; http://lattes.cnpq.br/9241045307171389; https://orcid.org/0009-0006-3506-046X; http://lattes.cnpq.br/1319231972690339; Leal Júnior, Arnaldo Gomes; https://orcid.org/0000-0002-9075-0619; http://lattes.cnpq.br/7246557168481527 ; Vimieiro, Claysson Bruno Santos; https://orcid.org/0000-0003-1916-0517; http://lattes.cnpq.br/0149542794493944Advances in motor rehabilitation have driven the development of technologies capable of interacting with the human body. In this context, exible actuators emerge as a promising alternative to rigid actuators, as they more closely resemble the behavior of natural muscles, enabling their application in wearable robotic joints for rehabilitation. This work presents the development of ber-constrained dielectric elastomer actuators (FCDEAs). Initially, static tests were conducted to evaluate the inuence of parameters such as pre-stretch, dimensions, and mechanical load on displacement and deformation. Subsequently, an optical ber in a serpentine con guration was embedded within the FCDEA, correlating optical power loss with displacement measured through image tracking techniques. A total of 36 tests were performed under varying geometric and mechanical conditions, along with oscillatory tests at di erent excitation ranges (0˘5V ;100mHz) and frequency-domain analyses using chirp signals and Bode diagrams. The results indicate that the developed actuators are capable of achieving 90% deformation, and the optical ber proves e ective for displacement measurement at low frequencies, showing good correlation between optical power and deformation, particularly at higher excitation amplitudes. Despite the limitations observed in static tests and the reduced accuracy of 69% in the Bode diagram, the dynamic analysis demonstrated the feasibility of the proposed approach for future applications in actuators and closed-loop control sensing systems.
- ItemTribocorrosão de metais duros em meios ácidos(Universidade Federal do Espírito Santo, 2025-08-27) Oliveira, Daniela Nunes; Mello, José Daniel Biasoli de ; https://orcid.org/0000-0001-8912-2132; http://lattes.cnpq.br/1696467778255755; Scandian, Cherlio ; https://orcid.org/0000-0002-4393-719X; http://lattes.cnpq.br/8466752738430250; https://orcid.org/0009-0009-2256-9445; http://lattes.cnpq.br/4437532644758347; Strey, Nathan Fantecelle ; https://orcid.org/0000-0002-2568-116X; http://lattes.cnpq.br/3613706957012460; Alves, Juliane Ribeiro da Cruz ; https://orcid.org/0000-0002-5766-6263; http://lattes.cnpq.br/3865682870831139Hardmetals are composite materials widely used in industrial applications that demand high wear resistance. Among them, WC–Co, composed of tungsten carbide particles embedded in a cobalt matrix, is the most common, being employed in cutting tools and components for the mining and oil industries. Despite their high wear resistance, their service performance can be compromised in corrosive environments, where the interaction between wear and corrosion accelerates degradation, making the study of tribocorrosion essential. Accordingly, this work investigated the tribocorrosion behavior of WC–Co composites with different cobalt contents (9%, 10%, and 16%) and carbide grain sizes (1.2 µm, 1.3 µm, and 2.5 µm) in acidic media, aiming to understand the interaction between sliding wear and corrosion and their effects on material integrity. The composites were characterized by chemical analysis, X-ray diffraction, grain size measurement, hardness, and density. Sliding wear, corrosion, and tribocorrosion tests were performed, with the latter two conducted in H2SO4 solutions at 0.01 N and 1 N. Synthetic hematite spheres were employed as counterbodies, chosen to simulate typical practical conditions, particularly in iron ore beneficiation. Analyses included friction coefficient determination, triboscopy, electrochemical parameters, mass loss, and surface characterization by optical microscopy, SEM, and EDS. In the sliding wear tests, the friction coefficient exhibited stable behavior (0.21–0.33), and wear rates were on the order of 10−4 mm3/m for the samples and 10−6–10−5 mm3/m for the spheres, without significant mechanical damage, such as grain fracture or pullout. In the corrosion tests, selective dissolution of the binder occurred in 0.01 N, with average mass loss around 0.07 mg/min for all samples. In 1 N solution, 09Co12 and 10Co13 showed average mass losses of 0.08 mg/min, whereas 16Co25 exhibited a significantly higher value of 0.17 mg/min, indicating lower corrosion resistance for the sample with the highest cobalt content. During tribocorrosion, the friction coefficient varied with polarization, and the sample with the highest cobalt content again exhibited the highest wear rates (10−2 mm3/m). SEM images revealed selective binder dissolution and the formation of a pseudopassive tungsten oxide layer, with a shallower dissolution depth than in isolated corrosion, suggesting partial sealing by redistributed corrosion products