Effect of high strain-rate deformation on surface mechanical properties of stainless steel after peening

This paper investigated the effect of high-rate deformation on the change of mechanical properties on the surface of metallic materials during a peening as a surface modification of metallic materials. Especially, we focused on the introduced compressive residual stress and the yield stress increase on the surface, which brings about the improvement of fatigue strength of the materials after peening. For this purpose, we compared the results using two different peening. One is a static indentation with a steel ball, and the other is a dynamic peening with high velocity. The residual stresses were obtained through the comparison with experimental depths using an elastic-viscoplastic finite element model for the peening, and the variation in yield stress was also obtained using indentation tests and numerical analysis of indentation tests. As a result, we clarified the effect of strain-rate on the variation in yield stress and induced residual stress. Especially, the compressive residual stress and the increments of yield stress of the surface layer within 600 μm depth after dynamic peening was larger than that after static peening.