Effects of Residual Stress Induced by Laser Shock Peening on Fatigue Crack Propagation Behavior in Directed Energy Deposition Stainless Steel

To investigate the effect of laser shock peening (LSP) on the fatigue crack propagation behavior of 316L stainless steel fabricated by directed energy deposition (DED), three‐dimensional finite element models of DED and compact tensile specimens before and after LSP are developed. The residual stress fields induced by DED and LSP are simulated, as well as the effects of different residual stresses on the stress intensity factor and effective stress ratio based on the contour integral method are also analyzed. The microstructure of the LSP region is observed by scanning electron microscope. When the crack length increases from 12 to 22.5 mm, the average effective stress ratio of the DED specimen is 0.133, and the average effective stress ratio of the DED specimen after LSP decreases to 0.110, which decreases by 17.3%. The fatigue lives of the DED specimen before and after LSP are 62.7% and 105.2% of that of the hot‐rolled plate. After LSP treatment, the fatigue life of the DED specimen is increased by about 1.68 times. The fracture morphology in the transient fracture zone changes from ductile and brittle mixed fracture to ductile fracture. Herein, the three‐dimensional finite element model of directed energy deposition and a compact tensile specimen before and after laser shock peening are first established. Then, the stress field distribution of the specimens is obtained by a combination of experiments and simulations. Finally, the influence rules of residual stress on the stress intensity factor and effective stress ratio are quantified based on the contour integral method.