Browsing by Author "Rodrigues, D. M."
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- Critical review on friction stir welding of aluminium to copperPublication . Galvão, Ivan; Loureiro, A.; Rodrigues, D. M.The status quo of aluminium-to-copper joining by friction stir welding (FSW) drastically changed in recent years, as a result of the increased interest of the scientific community on this subject. Actually, since 2006 a large increase in the number of research groups addressing Al–Cu FSW has been witnessed all over the world, together with a significant increase in the amount of published studies. A chronological perspective on the evolution in Al–Cu FSW research is provided in this work, highlighting the pioneer and original contribution of several researchers to the current knowledge on the subject. Detailed and comprehensive investigations on the material flow mechanisms, the phenomena governing the formation and distribution of intermetallic phases during Al–Cu FSW, their relations with the welding parameters and their impact on the morphological, structural and mechanical properties of the welds are thoroughly discussed. The main findings reported in the literature are summarised in thematic tables.
- Tensile properties of S355 butt welds after exposure to high temperaturesPublication . Rodrigues, D. M.; Leitao, Carlos; Balakrishnan, M.; Craveiro, Hélder D.; Santiago, A.The influence of the exposure to high temperatures on the tensile properties and failure mode of butt-welded connections in 5355 J2 steel was assessed. With this aim, welds were produced using GMAW and FCAW semiautomatic processes. Transverse tensile specimens were extracted from the welded coupons, heated to high temperatures (300, 600 and 900 degrees C), cooled to room temperature and then loaded to failure. Microstructural characterization and hardness measurements were performed to explain the tensile behaviour of the specimens after exposure to high temperatures. Tests at ambient temperature were also conducted for benchmark comparison. From the analyses, it was possible to conclude that, in the absence of welding defects, the residual properties of the 5355 joints, after heat exposure, are very similar to that of the base material. However, the presence of welding defects, depending on its severity and typology, may conduct to rupture in the welds and low residual strength, after heat exposure. This happens even if those defects not affect the tensile properties of the connections in the as-welded condition. The residual capacity of steel structures will be only severely reduced after heat exposure to temperatures in the eutectoid range, i.e., between 700 and 900 degrees C. The critical exposure temperature may vary according to the chemical composition of the steels/welds and to the duration of the heat exposure. The strength loss and the ductility of the BM and of the connections are dependent of the duration of the heat exposure. Very long exposure conditions conduct to a maximum decrease in residual yield and ultimate strength of 30 % and 20%, respectively, in S355 J2 steels and welds.