https://repositorio.ufu.br/handle/123456789/5467 2026-04-23T02:54:19Z 2026-04-23T02:54:19Z https://repositorio.ufu.br/handle/123456789/48591 2026-04-01T06:18:45Z 2024-02-29T00:00:00Z

Title: Dispositivo de resistência vibratório para treinamento muscular de membros inferiores Abstract: The practice of sports and physical exercise in general has a major influence on people’s fitness and quality of life. In this context, it is of fundamental importance to develop low-cost muscle training/rehabilitation equipment that is efficient and accessible. The aim of this study was to design, build and test a extension/flexion machine with a cam-spring resistance system and a device for applying mechanical vibration in the direction of muscle shortening. Two identical conventional extension chairs were purchased, one of which had its resistance system replaced by a cam-spring system with mechanical vibration and the other was kept completely original to be used in the tests as a basis for comparison, with identical postural parameters. The new equipment is simple, compact, low inertia and allows mechanical vibrations to be applied in the direction of muscle shortening with adjustable frequency and amplitude. Due to its low inertia design, the equipment also allows milimetric load variation and exercises to be performed at higher speeds and with less risk of injury. The comparative tests evaluated the activation amplitude of the electromyographic signal in the right and left rectus femoris muscles of trained individuals during bilateral extension/flexion movements on the conventional chair and the new equipment. The sample consisted of 7 trained male volunteers aged between 18 and 40. The protocol consisted of 4 types of exercise: conventional machine with controlled speed (CEC), new machine with controlled speed (CAME), new machine with controlled speed and addition of mechanical vibration (VIBRA) and new machine with maximum speed (POT). A significant increase in the amplitude of the electromyographic signal was observed in the POT compared to the other exercises, both in the concentric and eccentric phases. Overall, the equipment proved to be effective, safe and with great innovative potential for improving training gains.

2024-02-29T00:00:00Z https://repositorio.ufu.br/handle/123456789/48457 2026-03-04T06:26:10Z 2026-02-20T00:00:00Z

Title: Modelagem computacional de escoamentos turbulentos utilizando a metodologia da fronteira imersa dos volumes fantasmas Abstract: The capability to digitally simulate the physical world has transformed the manner in which science and engineering interact with nature. As one of the most challenging fields of this transformation, Computational Fluid Dynamics (CFD) has established itself as a fundamental pillar, enabling the high- fidelity representation of complex flows. However, within the scope of immersed boundary methods, the faithful representation of intricate interfaces and their efficient geometric processing remain critical challenges for the robustness and viability of current numerical tools. This thesis presents the development, extension, and improvement of the Ghost-Cell Immersed Boundary Method (IB-GCM) integrated into the MFSim computational platform. The work focuses on the solution and validation of flows involving dynamic and thermal effects, as well as fluid-structure interaction (FSI). The methodology was validated through classical cases, such as Poiseuille flow with thermal effects and flow in coaxial ducts, demonstrating sealing capabilities when using zero-thickness boundaries. Flow around a sphere was simulated in both laminar and turbulent regimes, applying Large Eddy Simulation (LES) closure models and utilizing Adaptive Mesh Refinement (AMR) to efficiently capture high gradients in the vicinity and wake of the sphere. In the context of FSI, the vibration of a submerged plate was validated, and the dynamic response of a clamped-clamped beam subjected to cross-flow was analyzed. Finally, a preliminary analysis of an injector applied to industrial-scale projects was performed. The results consolidated in this thesis ratify the IB-GCM method as a robust, accurate, and versatile tool, capable of addressing the complexity of coupled transport phenomena in complex geometries, bridging the gap between high-rigor academic research and the technological demands of modern industry.

2026-02-20T00:00:00Z https://repositorio.ufu.br/handle/123456789/48197 2026-02-06T06:26:57Z 2025-10-31T00:00:00Z

Title: Monitoramento do processo de manufatura aditiva por deposição à arco, utilizando algoritmo de aprendizagem e fusão de sensores Abstract: This work presents the development of a process-monitoring system for Wire Arc Additive Manufacturing (WAAM) to support the inspection stage of fabricated parts by predicting and indicating potentially defective regions. The solution integrates a data acquisition and instrumentation system, a machine-learning algorithm, sensor fusion, anomaly clustering, and cross-validation with radiographic imaging. The experimental plan comprised the deposition of walls in carbon steel and stainless steel, using different deposition strategies, controlled induction of instabilities, and the acquisition of time series for the process variables: welding voltage and current, shielding-gas flow rate, wire feed speed, travel (deposition) speed, arc luminous intensity, and deposition acoustic signals. Anomaly detection was designed through interactive analysis pipelines, a learning algorithm based on an LSTM Autoencoder, and two indicators of anomalous events: an Amplitude Threshold (large-magnitude events in the reconstruction error) and a Volatility Threshold (persistent fluctuation events). Subsequently, a sensor-fusion strategy and clustering (K-Means) of hybrid features (statistical and wavelet-based) were applied, together with dimensionality reduction (PCA), to obtain groups with signatures/profiles consistent with regions exhibiting an increased probability of defect occurrence. System validation was performed by overlaying the predictions onto the radiographic images of the fabricated parts, thereby enabling comparison between the regions indicated by the prediction system and the defective areas actually observed.

2025-10-31T00:00:00Z https://repositorio.ufu.br/handle/123456789/48169 2026-02-05T06:25:29Z 2025-12-15T00:00:00Z

Title: Aplicabilidade da metodologia da taxa de alívio de energia de deformação para determinação da tenacidade à fratura de ligas metálicas por indentação instrumentada Abstract: The determination of fracture toughness of ductile metals through the instrumented spherical indentation technique has been an alternative for characterizing in-service components—where sample removal is not possible—due to its semi-destructive nature and cost-effectiveness. Different mathematical models are presented in the literature as indirect estimates of this toughness. Zhang, Wang and Wang (2019b) introduced the first model based on the Energy Release Rate (ERR) concept of fracture mechanics and the ideas of continuum damage mechanics for assessing fracture toughness. The model determines the value of the J-Integral from the loading–unloading cycles of indentation. Like the other methodologies, the ERR methodology—despite being an indirect measure of fracture toughness—has the strongest basis in fracture mechanics and was the methodology chosen to be studied in detail in this work. During the development of studies to verify the applicability and limitations of the ERR methodology, some issues were observed, and thus alterations were proposed to correct the methodology and broaden its applicability and improve result accuracy. For the study, AISI 4340 steels with different microstructural compositions, AISI 4130M, API X65, X80 and X100 used in the oil and gas sector were selected. Additionally, to understand the model’s limits, the austenitic stainless steel AISI 304 and the aerospace alloy AA7050-T7451 were studied. The results were compared with values extracted from standardized fracture toughness tests, following ASTM E1820 and conducted at the Friction and Wear Technology Laboratory, as well as from the literature. It was observed that the JIIC value calculated by indentation showed a strong dependence on the indenter diameter, and to correct, the fracture toughness value must be multiplied by a factor C = (1/Di)^1,18 depending on the diameter used. Furthermore, to obtain the mode I fracture toughness, JIC, from JIIC, it is necessary to obtain the ratio α 2 = JIIC/JIC, assumed to be constant and equal to 0.35 for all metal alloys, a fact that did not hold true. Through the present work and the literature, values of α^2 and also its relation to the hardness of the studied materials were obtained, with the exception of API X100 steel. Thus, a function for estimating α was proposed: (i) α = f(HV), with R^2 = 0.99 for HSLA steels and (ii) more generally α = f(σy/E), with R^2 = 0.97 for all metal alloys. Applying the proposed corrections made it possible to obtain JIC values calculated from indentation tests with errors less than 12.8%.

2025-12-15T00:00:00Z