https://repositorio.ufu.br/handle/123456789/5466 2026-04-14T00:31:15Z https://repositorio.ufu.br/handle/123456789/48538 Title: ANDRADE, Rafael Moreira. Manufatura aditiva por deposição a arco para a recuperação de matrizes para injeção de alumínio sob pressão Abstract: Extending the service life of tooling in the high-pressure aluminum die-casting industry represents a technical and economic challenge, given the severity of the cycles to which these components are subjected. In this scenario, Wire Arc Additive Manufacturing (WAAM) emerges as a strategic alternative for the restoration of functional surfaces. The present study investigated the technical and metallurgical feasibility of applying WAAM for die repair, comparing the performance of three distinct alloys: Maraging 250 (solid wire), Martensitic Stainless Steel 420 (solid wire), and H13 Tool Steel (metal-cored wire). Initially, a decommissioned mold was characterized to identify the predominant failure mechanisms, thereby establishing the requirements to be met by additive manufacturing. The welding stability of the Maraging alloy was also investigated regarding three shielding atmospheres, while also varying two different deposition strategies. Maraging 250 steel stood out for its strength and structural integrity. The alloy benefited from the reheating thermal cycles intrinsic to the process, which promoted in-situ aging, resulting in a hardness gradient. In contrast, the martensitic alloys (Stainless Steel 420 and H13) showed high sensitivity to deposition strategies and cooling rates. It was observed that low heat input strategies resulted in the formation of untempered martensite, leading to brittle fracture. Implementing strategies aimed at heat accumulation enabled the processing of 420 Stainless Steel through the auto tempering mechanism, restoring the necessary ductility; however, this approach proved insufficient to mitigate cracking in H13 Tool Steel due to its high hardenability and segregation of brittle phases. Thus, thermal management is fundamental for the application of WAAM in tool steels, validating Maraging steel as the most robust solution for the remanufacturing of high-performance molds. 2026-02-26T00:00:00Z https://repositorio.ufu.br/handle/123456789/48527 Title: Desenvolvimento de equipamento e metodologia para avaliação do desempenho de rebolos aplicados na retificação tangencial em vidros Abstract: Glass grinding is an abrasive machining process widely employed in industry, in which grinding wheel performance and wear directly influence surface quality, dimensional stability, and production efficiency. In this context, the present study aimed at the development, instrumentation, and experimental validation of the TriboGlass test bench, designed to perform controlled accelerated wear tests of grinding wheels used in tangential glass grinding. The test bench was designed and built in partnership with Diamanfer and structured to enable continuous monitoring of the Material Removal Rate (MRR) as well as the main operational process variables. In parallel, a systematic methodology for grinding wheel wear assessment was developed, including mass loss measurements, three-dimensional geometric characterization through color map scanning, cross-sectional profile evaluation, and macroscopic surface inspection. Six experimental tests were conducted, in which initial transient regimes associated with the high aggressiveness of new grinding wheels were observed, followed by the progressive stabilization of the abrasive contact. Localized variations were also recorded due to operational events such as glass replacement, grinding wheel substitution, and mechanical interferences in the carriage displacement system. The monitoring system demonstrated high sensitivity in detecting such occurrences, confirming its reliability for continuous process evaluation. The results confirm the structural stability, repeatability, and operational robustness of the TriboGlass test bench, validating it as a reliable experimental platform for systematic test matrices and future investigations related to tribological mechanisms involved in glass grinding processes. 2026-02-27T00:00:00Z https://repositorio.ufu.br/handle/123456789/48467 Title: Identificação de desbalanceamento de máquinas rotativas usando metamodelagem cokriging Abstract: Along with misalignment, the leading cause of mechanical issues in rotating machinery is unbalance of the rotating assembly. Among the various balancing techniques available, the influence coefficient method is widely used. However, this technique demands test runs with trial masses, which is often inefficient, resulting in the need for new balancing attempts and prolonging service execution time. In the Oil and Gas industry, minimizing intervention time is paramount, directly translating to increased productivity and reduced lost profit, the financial loss due to the non-processing of oil derivatives. Specifically for refineries (downstream), where redundant (spare) machinery is often unavailable, any unscheduled intervention can lead to a complete unit shutdown. Therefore, exploring novel possibilities for unbalance detection without the need for trial mass runs is essential to significantly reduce the time required for these procedures. Thiswork addresses this context by implementing a balancing methodology without the use of test weights using a Cokriging Metamodel. This approach leverages two distinct data sources: experimental data, which consist of time-domain vibration signals collected directly from the machine (high-fidelity or expensive data), and numerical data, which are vibration signals generated from a numerical model (low-fidelity or cheap data). To validate the proposed methodology, two validation phases were conducted: a purely numerical validation and an experimental validation. For the numerical validation, vibration signals generated from a numerical model were utilized as high-fidelity samples and Monte Carlo uncertainty was added to stiffness and damping of the bearings and rotor modulus of elasticity in order to create the low-fidelity samples. For the experimental validation, tests were performed using a test rig (a rotor kit with two disks between bearings). Unbalance sets were applied in two planes (two disks) and vibration measurements in time domain were taken. Subsequently, this vibration data was divided into training and validation datasets and a cross-validation was performed. The experimental validation is a crucial factor in establishing the methodology, for instance, defining the optimal quantity of high-fidelity and low-fidelity samples to be included in the metamodel to maximize its performance. 2026-02-26T00:00:00Z https://repositorio.ufu.br/handle/123456789/48456 Title: Estudo da utilização de ciclones para separação de particulados do fluxo de syngas em um reator de gaseificação Abstract: This study investigated the performance of a syngas cleaning system applied to a gasification reactor, with a focus on the efficiency of particulate matter removal using cyclones. To compare theoretical efficiency prediction models with experimental results, a test bench was built consisting of a prototype cyclone, a blower, and a particle feeding system. Experimental tests were conducted using iron oxide and sand particles with their respective particle size distributions. The experimental results were compared with the classical collection efficiency models proposed by Lapple, Barth, Leith & Licht, and Dietz, allowing the level of agreement between theoretical predictions and experimental data to be assessed. The analysis showed that the models present significant differences among themselves, highlighting the importance of experimental validation. Among the evaluated models, the Leith and Licht model exhibited the best agreement with the experimental results, both for finer and coarser particles. A sizing and optimization software was developed to evaluate a large number of cyclone geometries and to select configurations with improved performance, considering simultaneously multiple efficiency models and the associated pressure drop. The selected cyclone presented a collection efficiency of 80.05% according to the Leith and Licht model. The application of cyclones operating in series was investigated as a strategy to enhance particle removal efficiency, with each subsequent cyclone fed by the material not collected in the previous stage. The use of two cyclones in series increased the overall collection efficiency to 91.04%, while an arrangement with four cyclones in series reached 96.67%. Configurations with five or more cyclones were not considered feasible due to limitations of the reactor internal space. Therefore, the four-cyclone series arrangement was defined as the most suitable solution, combining high collection efficiency with constructive feasibility. 2026-02-03T00:00:00Z