機械加工面の3軸残留応力のcos α法によるX線測定

抄録

In recent years, the cos α method attracts engineers as a new method of X-ray stress measurement using whole Debye-Scherrer rings recorded on two-dimensional detectors. The principle of the cos α method was first proposed by Taira, Tanaka, and Yamasaki for in-plane biaxial stress analysis, and later extended by Sasaki et al to the triaxial state of stresses. The method proposed by Sasaki et al utilizes several Debye-Scherrer rings taken at different incident angles of X-rays to determine traxial stresses. In the present paper, the cos α method was applied to measure triaxial residual stresses of uni-directionally machined surfaces of a carbon steel made by grinding, milling and planing. The recommended procedure for experimental measurement of out-of-plane shear stresses was proposed, together with a new method for determination of the normal stress perpendicular to the specimen surface. The incident angle of X-rays for stress determination is recommended to be larger than 35° and the normal incidence is for out-of-plane shear stresses. Out-of-plane shear stresses along the cutting direction which were characteristic of uni-directionally machined surfaces were increased according to the degree of cutting severity in the order of grinding, milling and planing. In-plane normal stresses were compressive, and the amount of compression was larger in the direction perpendicular to the cutting direction. Based on the stress values measured under different incident angles, the in-plane normal residual stress was suggested to increase near the surface. Out-of-plane normal stress determined by the new method was small compression.