Dynamic evolution of welding residual stress field under noncontact electromagnetic force

Controlling welding residual stress and distortion has still been a challenging problem due to the complexity of welding process. In this paper, a new technique with inductive electromagnetic forces has been reported for controlling welding residual stresses and distortion in welded thin plate. In order to get better understanding the associated mechanism, a hybrid three-dimensional finite element analysis, including electromagnetic force induction, welding, and electromagnetic force impact processes, has been performed to investigate the dynamic evolution of stress and strain in the welded plate under electromagnetic force impact. It is found that transient electromagnetic impact causes the mechanical response with the obvious strain rate sensitivity, and complex variation in stress and strain states in the welded plate occurs due to combination action of electromagnetic force and welding residual stress. As a result, the incompatible degree of strain field, arising from welding thermal cycle, is reduced. The residual stresses also finally fall, although the flow stress rises during electromagnetic impact. The measurement results of microhardness also indicate that the plastic strain state in local weld region is indeed changed under electromagnetic impact. Finally, continuous electromagnetic impacts experiments are conducted, and results show that this approach is very successful for reducing welding residual stresses and distortion in welded thin plates, without any impairment of appearance and performance.