1994 年 43 巻 490 号 p. 806-811
The stress measurement method with characteristic X-ray has been already estabilished as one of the most effective nondestructive evaluation methods of residual stress. However, the classical sin2ψ method with characteristic X-ray cannot evaluate accurately residual stress in the subsurface of metallic material which is treated with cold rolling or grinding, because the three-dimensional stress distribution or a steep stress gradient occurs in its subsurface. Therefore, various characteristic X-ray methods to evaluate the stress distribution have been proposed. This paper presents a new measurement method with polychromatic X-rays for residual stress along the depth direction in a subsurface layer. In this method, the surface stress and stress gradient in a subsurface layer is evaluated by using the theoretical equation describing the relationship between diffracted beam peaks of polychromatic X-rays and a strain distribution along the depth direction. Then, the stress distribution of a JIS SKS51 steel plate ground on its surface was measured as an example of applying this method. In consequence, it is confirmed that the residual stress distribution along the depth direction in a subsurface layer can be determined by using this method.