Shot-peening treatment is applied to the spring surface. The residual stress along the depth direction is evaluated with AutoMATE II. The figure shows that the compressive residual stress on the sample surface is equivalent to -410 MPa and the maximum compressive residual stress, at the depth of 60 microns from the sample surface, is equivalent to -600 MPa. It also shows that in the deeper areas than 60 microns from the surface the compressive residual stress is getting smaller and smaller along the depth direction, indicating the typical stress state for the shot-peening.
