Assessing the dwell time effect during friction stir spot welding of aluminum polyethylene multilayer sheets by experiments and numerical simulations

Abstract

Friction Stir Spot Welding (FSSW) is successfully applied for the joining of sandwich sheets with a polymeric core at varying dwell times. The mechanical performance of the joint is evaluated at various loading conditions. The joint performance of the sandwich sheet is significantly affected by the dwell time in the lap shear test and peel test, while a poor relationship exists between the dwell time and joint performance in the cross-tension test and uniaxial tension test. On the joint cross-section, macrostructure, microstructure, microhardness, and temperature are evaluated. A logical relation is established between these indexes and dwell time. A finite element model is developed to visualize and understand the material flow in the FSSW process of the sandwich sheet and to justify the accommodation of plasticized material into the core layer. The failure modes are also investigated via experiments and simulations, which matched with each other. The failure modes mainly depend upon the hook geometry.