Relaxation behavior of residual stress under mechanical loading investigated by neutron and X-ray diffraction

Akita, Koichi; Takeda, Kazuya*; Sano, Yuji*; Oya, Shinichi*

In this study, the relaxation process of the surface compressive residual stress under mechanical loading was analyzed using neutron and X-ray diffraction techniques and an elasto-plastic finite element model. The material used was a structural steel SM41 (Yield stress of SM41:Sy=286 MPa). The relaxation of the surface compressive residual stress was started at 187 MPa of tensile stress although the stress of the surface layer did not reach the yield stress, which would be caused by the re-distribution of the residual stress due to the plastic deformation of the center region. It was cralified that the Understanding of the magnitude and distribution of the balancing tensile residual stress was very important to evaluate the relaxation of the surface compressive residual stress against tensile applied stress.