Effects of Electric Current Pulse on Residual Stress in S355 Steel Subjected to Laser Surface Treatment
N. H. Gu, Y. Y. Hou, X. L. Han and P. Wang
S355 steel is used as the research object and the effects of the electric current pulse on residual stress in S355 steel are discussed in this paper. The laser surface treatment was used to produce the tensile residual stress on the surface of S355 steel specimen, which is used to simulate the residual stress produced by the welding process. The residual stresses in S355 steel specimens before and after the action of the electric current pulse were evaluated by the hole drilling method. The mechanism of residual stress relieving by the electric current pulse was discussed. The experimental results show that the high energy electric current pulse can effectively eliminate the lager tensile residual stress in S355 steel specimen. Increasing the treatment time of the electric current pulse can improve the relieving effect of residual stress. The difference between x-axial residual stress and y-axial residual stress becomes smaller by increasing the treatment time of the electric current pulse. In this case, the effect of residual stress relieving and homogenization can be improved by increasing the treatment time of the electric current pulse. The residual stress can be relieved when the sum of the external dynamic stress induced by the electric current pulse and the initial residual stress of the materials is more than the resistance for the dislocations motion. The residual stress relieving by the electric current pulse method is promising to be widely used in the industry.
Keywords: Laser, S355 steel, residual stress, electric current pulse, residual stress relief, residual stress homogenization