Prediction and characterization of residual stresses from laser shock peening

► Laser shock processing (LSP) produces beneficial, but highly variable, residual stress fields. ► X-ray diffraction measurements of LSP residual stresses provide only a coarse description of the stress state. ► Simple statistical characterization of the LSP-induced stress field provide a meaningful interpretation of the benefit of LSP. ► Effective numerical solution strategy is of critical importance in achieving accurate simulation of LSP processing. The use of laser shock peening (LSP) to enhance the fatigue resistance of metals offers several potential advantages over more conventional surface enhancement techniques such as shot peening, including deeper penetration of the residual stresses, more reliable surface coverage, and the potential for reduced microstructural damage. In the last decade, computational hardware and software resources have advanced to a state that permits numerical simulation of practical LSP processing at a reasonable level of detail, including complex geometric features, multiple and overlapping laser pulses, and intensity variations within the individual laser spots. This article offers some further developments in simulating LSP processes on a realistic scale, as well as some simple methods for distilling and interpreting results from such simulations. A key point of interest is the local variations in residual stress that occur within the processed region, which are quite sensitive to processing variables, and not easily measured experimentally. The simulations suggest that X-ray diffraction measurements of the residual stress field offer only a coarse description of the final residual stress field, and should be interpreted with some caution. We propose some methods for interpreting the simulation results statistically, to provide a clear but accurate characterization of the surface treatment and its effect on fatigue behavior.