By the numerical simulation and experiments,the process analysis of draw-bending and draw-trimming of the tailor-welded blanks (TWBs) with the thickness ratio 1.2 mm/0.8 mm are made,in which the effect of the blank holder force (BHF), friction factor and die profile radius,etc.on the springback are mainly investigated.The TWBs' springhack angle in the corner of punch and die,the total springhack angle and the sidewall curvature are surveyed in draw-bending and draw-trimming.And the welded line movement,the stress distribution in TWBs forming and their interact relationship are analyzed.The TWBs' springback in draw-bending and draw-trimming are badly influenced by the BHF,friction factor,die profile radius etc.,in which the BHF is the key factor;there is an intimate relationship between TWBs' draw-bending springback/draw-trimming springhack and welded-line movement,by which it will be advantageous to reduce the TWBs' springback through controlling the welded-line movement.In comparison,the TWBs' draw-trimming springhack is smaller than the TWBs' draw-bending springback,so it is better to use draw-trimming process for controlling TWBs' springback and improving the shape precision of TWBs' forming.

By simulation, the influence law on the strain path was researched in the fracture dangerous position on different blank holder force (BHF), in the forming of tailor-welded blanks (TWBs) square box. The strain path of tailor-welded blanks (TWBs) square box was controlled in the fracture dangerous point through adjusting value, distribution and variational mode of BHF, then the formability was improved. The results mainly show that the value and distribution of BHF on thick/thin blanks have significant influence on the forming strain path in the fracture dangerous position and the safety margin, and the proper distribution of BHF can change the fracture site and increase the forming limit depth. With the step BHF, the strain path is transferred from stretch-press strain state to double stretch state, and the safety margin is increased significantly. Variable BHF by multiple-area control is propitious to adjust sheet flowing in the die, and then the strain path of the dangerous point can be controlled better. The formability can be increased by altering the forming strain path in the dangerous position and adjusting the lurking fracture site.