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- Comparative analysis of welding processes using different thermoplasticsPublication . Trindade, Adelino; Guimarães, AndréThis study examined and contrasted three widely utilized welding techniques for modern thermoplastics: hot gas welding, laser beam welding, and friction stir welding. These techniques were employed to join various thermoplastic materials, particularly focusing on polypropylene, polyethylene, and polyvinyl chloride. The weld quality was evaluated using visual inspections and tensile strength tests. Additionally, Vickers hardness tests were performed on the welded joints to detect microstructural alterations. The research aimed to deepen the understanding of the mechanisms behind these welding processes and assess the welded joints' strength.
- Influence of Injection Conditions on Adhesion Interface in Sandwich PanelsPublication . Guimarães, André; Costa, Tiago; Trindade, Adelino; Carbas, Ricardo; Silva, L. daComposites are materiais combining a strong reinforcement with a lighter matrix for enhanced mechanical and thermal properties. A typical example is the sandwich panei, comprising sturdy outer layers and a lightweight core, such as rock wool, enclosed between them. The outer layers can be metal, wood, or plastic. In paneis with polyurethane (PUR) cores, the bond between the PUR and metal sheets can weaken over time due to stress and fatigue, potentially causing structural failure. Researchers are actively exploring methods to enhance PUR and metal sheet adhesion. Their studies encompass surface treatments, optimizing injection conditions, refining PUR composition, and computer modeling of the material interface [1, 2]. Studies by Pereira et al. [ I ] highlighted that primers significantly enhance adhesion, whereas Naik et al. [2] explored optimizing the production process through tests to ensure robust and long-lasting adhesion. This study investigated the adhesion of PUR adhesives to metal sheets under real-world production conditions. The paneis were produced in a factory environment using ali the parameters and procedures to create a fundamental part. The study aimed to identify and categorize common adhesion defects (e.g., voids, weak adhesion) that may occur during production, additionally, it aimed to develop corrective actions to prevent these defects. The study involved performing pull-out tests on specimens taken from different positions on a large board and comparing the results with reference specimens without defects.
- A Importância Da Soldadura De Termoplásticos: Um Estudo De Comparação De Processos Com Caraterísticas DistintasPublication . Trindade, Adelino; Guimarães, AndréTrês dos processos de soldadura mais utilizados na ligação de termoplásticos modernos foram analisados e comparados neste trabalho, concretamente a soldadura por gás quente (HGW), a soldadura por raio laser (LBW) e a soldadura por fricção (FSW). Os processos referidos foram utilizados na soldadura de vários materiais termoplásticos distintos, dando foco em apenas três desses materiais, tais como: polipropileno (PP), polietileno (PE) e policloreto de vinil (PVC). A qualidade obtida nas diferentes soldaduras foi avaliada recorrendo a uma análise visual, bem como através de ensaios de resistencia a tracção. Foram também realizados ensaios de dureza de Vickers ás juntas soldadas, que revelaram algumas alterações microestruturais. O estudo efetuado teve como finalidade melhorar o conhecimento dos mecanismos envolvidos na execução dos processos de soldadura utilizados e na análise da resistência das juntas soldadas.
- Influence of Continuous Laser Beam Welding Parameters on Welding Quality of a Structural SteelPublication . Coelho, Gonçalo; Trindade, Adelino; Guimarães, AndréThis study investigates how key laser welding parameters affect keyhole welding under continuous wave conditions. In particular, the relationship between laser power and focal position, and their interaction with other process variables, plays a critical role in achieving optimal thermal cycles and temperature distribution in the weld seam and heat-affected zone. The study also compares theoretical temperature distributions with experimental measurements to validate the applied thermal models. Weld bead characteristics were evaluated by analyzing the surface finish of the top and bottom sides of the weld. Weld quality was assessed through tensile testing, thermal analysis, and microstructural evaluation. The results demonstrate that slight variations in focal height and power significantly affect the dynamics and geometry of the weld pool. Although negative focal heights improved penetration, they also increased porosity, spatter, and oxidation due to excessive gas formation. Despite these challenges, all samples achieved full penetration, with tensile fractures occurring outside the fusion zone. The study also shows that the focal position relative to the material surface influences energy distribution, molten metal flow, and spatter formation. These factors affect how molten metal moves inside the keyhole and reaches the bottom surface of the weld bead, helping prevent gas entrapment. The findings highlight the importance of parameter optimization in balancing penetration depth and surface quality. Future research should explore real-time monitoring, computational modeling, and alternative shielding gas configurations to improve welding performance.