Dislocation-based study on the influences of shot peening on fatigue resistance

Shot peening technology is widely used to enhance the fatigue resistance of mechanical parts exposed to the cyclic loadings. The residual stress, grain refinement, work hardening and surface roughness are the four major results of shot peening, which play the important role in enhancing effects of fatigue performances. A framework linking the dislocation-based finite element simulation to the Navarro-Rios model (N-R model) was developed to evaluate the fatigue resistance of shot-peened materials. The parametric three-dimensional finite element models of multiple shot impacts, embedded with the dislocation density-based constitutive model, were developed firstly. The predicted residual stresses, grain refinements, surface topographies and surface roughnesses are all in good agreement with the experimental results. The simulation results of shot peening were then imported into the N-R model to analytically evaluate the stresses for fatigue crack arrest and corresponding values of crack tip opening displacement (CTOD). The computation results show that the S110 shots can effectively improve the stresses for the surface crack arrest, while the more grains within the shot-peened surface and subsurface are endowed with the larger stresses for crack arrest by S230 shots, and the double shot peening (S230 + S110 shots) takes the advantages of the cases of S230 and S110 shots.