Modeling approach and deformation behavior of a tailor-welded tube in hyfroforming

The flow stresses of the heat affected zone(HAZ) of the STKM11A welded tube are determined by an empirical law based on the Vikers Hardness(HV) distribution in circumferential direction of the tube.Finite element model including the weld and the HAZs of the welded tube in hydroforming is made by slicing the HAZ into strips with various flow stresses.The deformation behavior including the bulged profile in cross-section,wall thickness distribution in circumferential direction forming limit and so on is investigated by using the new model and compared with experimental results.The results show that the cross-section of the welded tube can not maintain a circular profile during the hydroforming,and a non-uniform thickness distribution in circumferential direction is observed with the minimum thickness locating within the HAZ.The results also imply that the new model can predict the deformation behavior,maximum pressure,and the potential burst location of the welded tube in hydroforming more accurately than other common models.