Comparing the weld zone representation methods during the formability prediction of friction stir welded blanks

During formability prediction of friction stir welded (FSW) blanks, it is necessary to incorporate nugget zone (NZ) and heat affected zone (HAZ) properties separately for better accuracy. In general, it is observed that the weld zone in FSW blanks is represented as a single entity, where in only global weld zone properties are implemented. But, the nugget zone and HAZ properties are not same and the property difference depends on the welding parameters during FSW. It is advisable to model the weld zone by incorporating the nugget zone and HAZ properties separately. In this work, the validity of weld zone representation, i.e., single zone or double zone under varied weld conditions of FSW blanks with equal and unequal thicknesses is explored. The domain of weld conditions, wherein single zone assumption breaks down will be identified. A comparison is done between the weld zone representation methods in FSW blanks with equal and unequal thickness sheets. The changes obtained in the weld zone methods are also analyzed. It is found that the number of single zone models has increased in transverse weld orientation and number of double zone models has increased in longitudinal weld orientation. This is mainly due to the change in failure location during forming of FSW blanks.