X線による残留応力分布測定法について

Abstract

Stress measurement by X-ray diffraction has certainly definite advantages. It is the only nondestructive method of determining the residual stress in metallic materials. Another feature is the fact that the localized stress can be measured by this method.In the field of mechanical and structure engineerings, it is said that residual stress in products is the problem of importance in the process of production and also in performance. The distribution of residual stress in these materials is in many cases determined by employing the destructive method, although this method has a little reliability in view of experimental procedure and has adaptability to very limited sort of materials.Recently the experimental technique of X-ray stress measurement has been surprisingly improved in our country and the field of its application is very much enlarged.In this connection, in the present paper, some methods of determination of residual stress by means of X-ray diffraction are demonstrated, by taking examples of specimen in the shape of plate and cylindrical bar. The equations for the calculation of residual stress are as follows:(1) plate (the case of symmetrical residual stress distribution)where σ: residual stress at a distance a from surface. σX: measured residual stress by X-ray at the layer a. h: thickness of plate.(2) plate (the case of unsymmetrical residual stress distribution)where σ: residual stress at a distance a from the top surface.σX: measured residual stress by X-ray method at the layer a.σbs: initial residual stress at the bottom surface.σba: residual stress at the bottom surface after removing the depth a.(3) cylindrical barwhere σz, σt, σr: axial, tangential and radial direction residual stress at the radius r.σzX, σtX: axial and tangential direction residual stress by X-ray method at the radius r after removing from surface a to r.It has been found from the result of present study that among the past investigations on the measurement of residual stress by means of X-ray are many problems open to questions about interpretation of the obtained results.