https://repositorio.ufu.br/handle/123456789/5146 2026-09-11T10:13:09Z 2026-09-11T10:13:09Z https://repositorio.ufu.br/handle/123456789/50201 2026-09-11T06:18:32Z 2026-08-03T00:00:00Z

Title: Desenvolvimento e avaliação de um sistema para sincronização da alimentação de arame pulsada com a corrente de soldagem no processo TIG Abstract: Pulsed (dynamic) wire feeding can modify the weld pool, metal transfer and heat input in arc welding processes. However, although some commercial solutions already exploit such technologies, they rely on proprietary feeders and/or torches. Furthermore, studies evaluating wire pulsation synchronized with the welding current remain scarce, which also motivated the development of this thesis. Thus, the objective of this work was to develop and evaluate a device compatible with conventional feeders and torches and with independent adjustment of frequency and amplitude for wire feed pulsation in the TIG process and to investigate the effects of synchronization between wire feed pulsation and current on the resulting deposits. The work methodology was organized into sequential stages. First, a pulsation device was built and characterized based on the cyclic deflection of part of the wire conduit. Next, a working envelope for the TIG process with pulsed wire feeding was established. Synchronization between wire pulsation and current was then implemented based on the electrode-to-wire voltage. The effects of wire pulsation parameters and current mode on bead geometry were subsequently evaluated. Finally, geometric, metallurgical, chemical, and thermal characteristics of the deposits produced. Characterization of the pulsation device demonstrated pulsation amplitudes of 2 to 15 mm at frequencies of up to 25 Hz, with tolerance for different wire materials and diameters. The pulsed feeding modified the bead geometry, being wire pulsation frequency the parameter with the greatest influence and wire stubbing (contact of the wire tip with the base metal at the bottom of the weld pool) the operational limiting factor at low current and high wire feed speed under constant current. The synchronization system achieved latency below 10 ms and enabled stable operation at boundaries previously unviable under constant current with pulsed feeding, thereby expanding the process working envelope. Under pulsed current synchronized with pulsed wire feeding, increasing frequency from 2 to 15 Hz reduced bead width approximately by 20%, penetration by 17%, and dilution by 20%. In the evaluation with the ER2594 wire, synchronization enabled an approximately 30% increase in wire feed speed compared with the limit achieved with constant current and pulsed feeding under an equivalent welding energy. Furthermore, synchronization yielded deposits with larger width and reinforcement, lower penetration and lower dilution, better preservation of Cr and Ni, with no relevant differences in hardness and ferrite/austenite balance. Thus, it is concluded that the developed device, combined with the synchronization strategy, can increase deposition capacity and improve deposit characteristics, opening up prospects for applications such as cladding and additive manufacturing, for instance.

2026-08-03T00:00:00Z https://repositorio.ufu.br/handle/123456789/50165 2026-09-10T06:21:18Z 2026-08-11T00:00:00Z

Title: Torneamento de Ti6Al4V com ferramentas texturizadas por laser de femtossegundos Abstract: The machining of the Ti-6Al-4V titanium alloy presents significant challenges due to its high specific strength, low thermal conductivity, high chemical reactivity, strong tendency toward adhesion, and accelerated cutting-tool wear. In this context, surface texturing of cutting tools has been investigated as a promising strategy for modifying the tribological conditions at the tool–chip and tool–workpiece interfaces and improving machining performance, particularly by extending tool life. Therefore, this study aimed to investigate the influence of microtextures produced on the rake face of cemented carbide tools during the turning of Ti-6Al-4V, evaluating their effects on machining forces, workpiece surface roughness, and tool life. The study was conducted in three experimental stages. In the first stage, different microtexture geometries were evaluated through an experimental design to identify the geometric parameters with the greatest influence on the machining process. At this stage, some configurations significantly improved the surface finish, reducing the average surface roughness (Ra) by up to 41.94% compared with the untextured tool, in addition to reducing machining forces by up to 8.64%. In the second stage, the geometric parameters of the selected textures were refined to optimize the microgroove geometry. The results indicated that certain configurations provided additional reductions in cutting forces, reaching a decrease of 8.02% compared with the conventional tool, as well as a 6.80% reduction in surface roughness. In the third and final stage, the optimized texture geometry was compared with an untextured tool and with textured-tool variants containing MoS₂ solid lubricant under finishing and roughing conditions. The results showed that, under finishing conditions, textured tools without lubricant reduced machining forces by 4.3%, whereas, under roughing conditions, the combination of texture and MoS₂ resulted in reductions of up to 57.9% in machining forces. Regarding surface roughness, improvements of up to 8% were observed during finishing, depending on the machining condition. Tool-life analysis indicated that textured tools without solid lubricant exhibited the best overall performance, achieving greater volumes of removed material before reaching the end-of-tool-life criterion, with average increases of 58% under finishing conditions and 24% under roughing conditions.

2026-08-11T00:00:00Z https://repositorio.ufu.br/handle/123456789/50156 2026-09-09T06:18:19Z 2026-08-08T00:00:00Z

Title: Detecção de anomalias nas respostas de vibração de rotores usando técnicas de inteligência artificial Abstract: Rotating machinery plays an essential role in industrial sectors such as oil and gas, power generation and mining, and its failures may result in unplanned shutdowns, significant economic losses and safety risks. Vibration analysis stands out as one of the main condition monitoring techniques, enabling the early identification of mechanical problems and supporting predictive maintenance strategies. The increasing adoption of continuous monitoring systems has led to large volumes of data, imposing limitations on traditional approaches based exclusively on manual analysis. This dissertation proposes and evaluates Machine Learning methodologies for anomaly detection in rotor vibration responses, with emphasis on unsupervised strategies aligned with the industrial reality of scarce labeled fault data. The work integrates and extends the Edge Analytics framework, developed by the Structural Mechanics Laboratory of the Federal University of Uberlândia (LMEst - UFU), which combines simple statistical techniques and deep learning models for anomaly detection. In addition to the original models of the Edge Analytics architecture—Gates, Autoencoder, DeepAnT, and Histogram — new models based on Multilayer Perceptron (MLP) and Long Short-Term Memory (LSTM) are developed and evaluated. Furthermore, the combination of these models with Change Point Detection (CPD) techniques is investigated in order to enhance sensitivity in identifying subtle and sustained changes in vibration responses. The validation of the proposed methodologies is conducted through five benchmarks, involving numerical and experimental data from different rotating systems, including rotors supported by magnetic bearings, an industrial exhaust fan and bearing degradation tests. Performance is assessed using classical classification metrics, with emphasis on the F1 score due to the strong class imbalance. The results indicate that there is no universally superior model, however LSTMand MLP-based models stand out in faults with progressive evolution, while the combination with CPD contributes to the detection of subtle changes. Thus, the study provides technical support for industrial applications in predictive maintenance.

2026-08-08T00:00:00Z https://repositorio.ufu.br/handle/123456789/50113 2026-09-05T06:21:15Z 2026-08-13T00:00:00Z

Title: Aumento de potência com baixo custo através de indução forçada com turbocompressor centrífugo em motor da década de 90 Abstract: The average age of the Brazilian vehicle fleet has been steadily increasing, which sustains a significant market for modifying vehicles from the 1990s and 2000s for recreational use. Engines from this period, designed as naturally aspirated units, have their power output limited by the intake air mass flow rate, a constraint that can only be overcome by increasing intake air density. This work presents the design, fabrication, installation and calibration of a forced induction system based on a centrifugal turbocharger applied to a BMW M50B25TU engine, converted to hydrous ethanol and managed by a Speeduino open-source programmable engine control unit, aiming to double the original power output and sized for an intake gauge pressure of up to 100 kPa. The use of components available on the Brazilian used- parts market was adopted as a cross-cutting design constraint, in order to ensure low cost and replicability. The sizing procedure covered the fuel system, the compressor, the turbine housing, the wastegate valve, the exhaust manifold, the pressurised piping and the intercooler, with analytical verification of each component. Tests were carried out on an inertial roller dynamometer developed during the project, across four successive configurations: baseline, ethanol and programmable engine management conversion, boosted operation at 25 kPa, and boosted operation under electronic boost control. A progressive performance improvement was observed, rising from 201.3 hp and 261.2 N·m in the baseline configuration to 409.2 hp and 489.7 N·m in the final configuration. Ignition timing was maintained at maximum brake torque under all wide-open-throttle conditions, with no knock limitation, confirming the margin provided by hydrous ethanol in an engine with a 10:1 compression ratio. The first failure observed was clutch slippage, a non-destructive failure mode anticipated during the design phase. The metrological limitations of the dynamometer are discussed, whose evidence of overestimation restricts the validity of the results to relative comparison between configurations.

2026-08-13T00:00:00Z