Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution Non-Commercial, que permite uso, distribuição e reprodução em qualquer meio, sem restrições desde que sem fins comerciais e que o trabalho original seja corretamente citado.Recebido: 31 Ago.Resumo: O presente trabalho consiste na investigação dos parâmetros de soldagem a ponto por fricção (FSpW) -velocidade de rotação (VR), tempo de soldagem (TS) e profundidade de penetração (PP) -de chapas de AA2198-T8 com 1,6 mm de espessura. O estudo foi realizado com base em ensaios mecânicos de cisalhamento das juntas sobrepostas soldadas nas condições indicadas pelo método Taguchi, visando à determinação da condição ótima de soldagem do ponto de vista de propriedades mecânicas e de processo. Os resultados obtidos indicaram que todas as condições de soldagem avaliadas excedem o limite de carga em cisalhamento mínimo requerido para aplicação aeronáutica. A análise também apontou que as variáveis VR e PP são responsáveis por quase 90% da variação da carga de cisalhamento das juntas, enquanto a contribuição do TS mostrou-se consideravelmente menos significativa. Por fim, a condição ótima de soldagem foi encontrada para os valores mais altos de VR e PP, considerando-se os intervalos dos parâmetros empregados no estudo.
Palavras-chave:Soldagem a ponto por fricção; FSpW; AA2198-T8; método Taguchi.Abstract: This work features the investigation of the refill friction stir spot welding (RFSSW) parameters -rotational speed (RS), welding time (WT) and plunge depth (PD) -of AA2198-T8 1.6-mm thick sheets. The study was performed based on lap shear strength tests of overlapped joints welded under conditions indicated by the Taguchi method in order to determinate the optimized combination of parameters, considering the mechanical properties and process conditions. Results based on mechanical testing indicate that all the welding conditions evaluated in the current study exceed the minimum criterion for lap shear strength required for aeronautic applications. RS and PD have shown to be responsible altogether for almost 90% of the welds' lap shear strength variation, while TS presents considerable less significant contribution to the joints' resistance. The optimized welding condition was found for highest RS and PD levels and lowest TS.
Abstract. Constrained Friction Processing (CFP) is a novel solid-state technique suitable to produce rods especially from lightweight materials. The technology is particularly interesting to overcome the processing challenges associated with Mg due to its hexagonal close-packed (hcp) structure. The process is a variation of the refill friction stir spot welding (refill FSSW) technique, and is performed by plunging the rotating shoulder into the base material, which causes the material to be extruded into the cavity crated by the retraction of the rotating probe and, at the same time, being constrained by it. The complex shear and the heat generated during the process causes metallurgical transformations in the material, such as dynamic recrystallization, allowing for substantial grain refinement to micro- or even submicro- scale. In this study, real time data – torque, axial force and temperature – acquired from the process are analyzed in order to present, for the first time, a description of the CFP technique. Furthermore, the resultant features of the microstructure of a refined rod is explored.
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