DSpace Community:https://repositorio.ufu.br/handle/123456789/51462026-06-21T03:13:09Z2026-06-21T03:13:09ZAvaliação da suscetibilidade à fragilização por hidrogênio em aços avançados de alta resistência aplicados na indústria automotivahttps://repositorio.ufu.br/handle/123456789/487572026-06-16T06:23:11Z2026-03-06T00:00:00ZTitle: Avaliação da suscetibilidade à fragilização por hidrogênio em aços avançados de alta resistência aplicados na indústria automotiva
Abstract: Hydrogen embrittlement has become a major challenge in the application of advanced high-strength steels (AHSS) in the automotive industry. Hydrogen uptake may occur throughout the material lifecycle, particularly during pickling, annealing, galvanizing, welding, and phosphating processes. The issue becomes more critical under mechanical shearing conditions, since the high dislocation density and microvoids generated at sheared edges promote localized hydrogen accumulation and abrupt fracture. Therefore, evaluating hydrogen effects under sheared-edge conditions is essential to assess the susceptibility of AHSS to hydrogen embrittlement. In this study, the hydrogen embrittlement behavior of DP1200 and TRIP1000 steels was investigated considering different edge-cutting conditions obtained by varying the punching clearance. A new methodology was proposed to enable ex-situ hydrogen charging at controlled levels, followed by constant load (CLT) and slow strain rate (SSRT) mechanical testing. Increased cutting clearance, associated with greater local deformation and the presence of microvoids, resulted in higher susceptibility to hydrogen embrittlement in both steels. Under favorable cutting conditions (12% clearance), the critical hydrogen contents were 0.27 ppm for DP1200 and 0.61 ppm for TRIP1000. However, when the clearance was increased to 25%, corresponding to reduced edge‑stretching capability, the critical hydrogen thresholds dropped significantly, reaching levels below 0.27 ppm for DP1200 and 0.24 ppm for TRIP1000. These findings highlight the importance of strict edge‑quality control, particularly for electro‑galvanized products. In this context, especially for DP1200, which showed greater sensitivity to this failure mode, post‑processing strategies, such as thermal desorption treatments, may be required to reduce hydrogen content and mitigate edge‑cracking risk during the service. The hydrogen effect on fatigue and weldability was also assessed. Stress‑controlled fatigue tests revealed hydrogen‑assisted embrittlement in both steels, although fatigue‑life reductions were more consistent for DP1200. Early crack nucleation was linked to the enhanced interaction between hydrogen and inclusions, which functioned as preferential initiation sites. In resistance spot welds (RSW), hydrogen promoted more brittle fracture modes without significantly affecting joint strength. Overall, these findings contribute to advancing the understanding of hydrogen embrittlement mechanisms in AHSS designed for automotive applications.2026-03-06T00:00:00ZAvaliação de pré-formas multimateriais em aço carbono e aço inoxidável austenítico depositadas via manufatura aditiva por deposição a arcohttps://repositorio.ufu.br/handle/123456789/487042026-05-19T06:34:58Z2026-02-27T00:00:00ZTitle: Avaliação de pré-formas multimateriais em aço carbono e aço inoxidável austenítico depositadas via manufatura aditiva por deposição a arco
Abstract: In this work, the metallurgical evaluation and adhesion at the interface between carbon steel and stainless steel in clad and multimaterial pre-forms (walls) produced by wire-arc additive manufacturing (WAAM) are carried out. Two walls were produced using AWS A5.18 ER70S-6 wires as the base material and AWS A5.9 ER309LSi as the coating material, through coordinated deposition with two welding robots operating in parallel. The walls differed exclusively in terms of the distance between the deposition torches, adopting spacing of 50 mm and 100 mm, keeping all other process parameters constant. The evaluation of the adhesion and integrity of the clad interface was carried out by guided bending tests according to ASTM A264:2019, using bending up to 180°, with the coating maintained in compression. The metallurgical characterization was conducted by optical microscopy, scanning electron microscopy and Vickers microhardness tests, allowing the analysis of the base material, the interface and the coating. The microhardness maps were obtained according to ASTM E384:2011, allowing the evaluation of hardness gradients along the clad interface. The results allowed to correlate the microstructural characteristics and microhardness profiles with the behavior observed in the bending tests, evidencing the influence of the distance between the deposition torches on the formation of the interface and on the integrity of the metallurgical bond between the stainless-steel coating and the carbon steel base material produced by additive manufacturing by arc deposition.2026-02-27T00:00:00ZDesenvolvimento de uma metodologia de instrumentação e avaliação da integridade de estruturas de concreto armado em operação contínua via técnica da impedância eletromecânica e o auto codificador variacional.https://repositorio.ufu.br/handle/123456789/486612026-04-30T06:25:42Z2022-07-28T00:00:00ZTitle: Desenvolvimento de uma metodologia de instrumentação e avaliação da integridade de estruturas de concreto armado em operação contínua via técnica da impedância eletromecânica e o auto codificador variacional.
Abstract: The monitoring of civil structures that are in full operation has been gaining more
and more space in Brazil and worldwide, due to large structures such as bridges,
viaducts, and dams that are reaching the end of their useful lives and need periodic and increasingly frequent maintenance. The advancement in the studies of
Structural Integrity Monitoring (SHM) and Artificial Intelligence (AI) has opened a
wide range of applications in monitoring structures and making possible increasingly accurate and robust diagnoses, especially in the construction sector. In this
context, this paper presents a methodology for instrumentation and evaluation of a
reinforced concrete structure that is in continuous operation, using the techniques
of ISHM (Structural Integrity Monitoring based on Electromechanical Impedance
Technique), ultrasound and AI. For this, the proposed methodology was applied
in detail to a reinforced concrete beam that supports a mezzanine at the Laboratório de Mecânica de Estruturas Prof. José Eduardo Tannús Reis (LMEst-UFU).
The results showed how important the methodology was to identify and separate
situations in which alarms from structure monitoring systems could present FalseNegatives and make correct decisions about the possible measurement limits for
a given structure. Thus, the objective was satisfactorily achieved and several suggestions for future work were presented.2022-07-28T00:00:00ZModelling and analysis of fluid flow problems coupled with radiative heat transferhttps://repositorio.ufu.br/handle/123456789/486332026-04-16T06:18:30Z2025-08-21T00:00:00ZTitle: Modelling and analysis of fluid flow problems coupled with radiative heat transfer
Abstract: Combustion plays a fundamental role in society, being one of the primary means of energy conversion and storage, with countless applications. As such, it is a key topic in engineering and industrial processes. In many cases, combustion and thermal radiation occur simultaneously: the high temperatures resulting from exothermic reactions, as well as the radiative interaction of the gases generated from these reactions, create an environment where complex radiative heat transfer takes place. Therefore, coupling CFD with radiative heat transfer models is essential for the accurate simulation of industrial reactive flows.
Furthermore, literature shows that thermal radiation can significantly affect heat transfer in other situations, such as in thermal cavities at ambient temperature, a problem that is frequently studied without considering radiation effects.
This work presents the development and benchmarking of a coupling between a CFD software (MFSim) and a radiative heat transfer solver for participating media (RTS), both internally developed by MFLab in the Federal University of Uberlândia. MFSim is a robust simulation package, capable of modelling turbulence, heat transfer, fluid–structure interactions, reacting flows, and Lagrangian particle transport. RTS is capable of modelling radiative transfer in gray and non-gray participating media containing gases like CO2 and H2O, as well as isotropic and anisotropic scattering phenomena.
By integrating these codes, the extensive set of physical models available in MFSim, designed to simulate complex engineering problems, now includes radiative heat transfer, enabling more realistic and accurate modelling of combustion processes. The coupling employs distinct meshes for CFD and radiation, connected via interpolation, allowing for more computational efficiency, as radiative models do not usually require the same spatial resolution as CFD. Tests have shown that the interpolation layer between both algorithms has relatively low computational cost. Benchmarks performed on canonical cases show good agreement with the literature, verifying the approach and reinforcing the importance of radiation in heat transfer simulations.2025-08-21T00:00:00Z