Effect of Plastic Deformation on Fatigue Crack Closure Behavior in Low Yield Strength Material and Its Welded Joint

Abstract

Crack closure behavior in fatigue crack propagation process was induced by plastic deformation near crack. In the paper, the effect of plastic deformation on fatigue crack closure in low strength material and its welded joint was studied.The results are as follows. Crack closure would be caused by plastic deformation near crack surface. Generally, crack opening ratio in high yield strength material is higher than that in low yield one. This tendency based on the degree of deformation near crack surface. In addition, in welded joint, crack propagation rate was higher than mother metal, though crack opening ratio showed almost 1 by the effect of residual stress. This could be explained by the effect of restrain for plastic deformation, which was induced by existence of compresive stress field ahead of crack.