https://repositorio.ufu.br/handle/123456789/5467 Mon, 13 Jul 2026 16:29:54 GMT 2026-07-13T16:29:54Z https://repositorio.ufu.br/handle/123456789/48786 Title: Degradação de revestimentos poliméricos aplicados em tubulações de esgoto Abstract: Urban sewer pipelines operate under severe conditions, including chemical corrosion, microbiological degradation, and abrasive wear. Metallic materials such as ASTM A36 carbon steel are highly susceptible to corrosion, especially in acidic, sulfide-rich environments, leading to material loss and reduced infrastructure service life. To mitigate these effects, the use of polymeric coatings has been widely adopted, although their performance under combined corrosion-abrasion conditions is not yet fully understood. This research proposes an integrated experimental methodology to evaluate the degradation of polymeric coatings applied to ASTM A36 steel, using a synthetic medium representative of urban sewage from Uberlândia (MG). Coal tar-epoxy and Zebron® coatings were tested, with nominal thicknesses of approximately 0.25, 0.50, and 1.00 mm. Electrochemical characterization was performed through open circuit potential (OCP) measurements, potentiodynamic polarization curves, and electrochemical impedance spectroscopy (EIS). Uncoated steel exhibited corrosion potentials below −0.50 V, high corrosion current densities on the order of 10⁻⁴ A·cm⁻², and charge transfer resistances (Rct) below 10² Ω·cm², indicating a high degradation rate. In contrast, polymeric coatings exhibited coating resistance (Rcoating) values of 10⁴ Ω·cm² at higher thicknesses (0.5 mm and 1.0 mm), demonstrating effectiveness in protecting the steel. The Zebron® coating maintained Rcoating values between 10³ and 10⁴ Ω·cm² after 168 h of immersion, especially near 1.00 mm thickness. The coal tar-epoxy coating showed progressive degradation over time, particularly at thicknesses below 0.50 mm. Abrasive wear tests using a rubber wheel in a wet medium revealed greater thickness loss for coal tar-epoxy, reaching approximately 0.05 mm after 8 hours, while Zebron® showed losses below 0.015 mm under similar conditions. The analysis revealed that reduced coating thickness decreases corrosion resistance due to the interaction between abrasion and corrosion, affecting long-term coating durability. Mon, 23 Feb 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/48786 2026-02-23T00:00:00Z https://repositorio.ufu.br/handle/123456789/48757 Title: 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. Fri, 06 Mar 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/48757 2026-03-06T00:00:00Z https://repositorio.ufu.br/handle/123456789/48661 Title: 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. Thu, 28 Jul 2022 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/48661 2022-07-28T00:00:00Z https://repositorio.ufu.br/handle/123456789/48591 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. Thu, 29 Feb 2024 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/48591 2024-02-29T00:00:00Z