Numerical modelling and experimental investigation of thermal and material flow in probeless friction stir spot welding process of Al 2198-T8

A finite element model based on software Abaqus/Explicit and experimentation was established to describe the probeless friction stir spot welding process of 2198-T8 aluminium alloy. An Arbitrary Lagrangian-Eulerian method was adopted in this model in which the Johnson-Cook equation was used to describe the flow stress depending on temperature, plastic strain and strain rate. The experimental results revealed the representative microstructure of the joint which has three typical zones: stir zone, thermo mechanically affected zone and heat affected zone. The relationship between the temperature field and dwell time was investigated based on the accurate description of temperature field. A model of the material flow was developed based on the numerical and experimental results.