1977 年 26 巻 280 号 p. 11-17
In the previous paper, the constant ψ method with ten angles incidence by using an X-ray diffractometer has been recommended for the X-ray stress measurement of austenitic stainless steel. This method, however, requires a very long time for the measurement, and furthermore cannot be applied to actual measurement of large machine parts. In the present study, therefore, the constant ψ0 method with oscillation technique by using an X-ray diffraction stress analyzer was applied to the residual stress measurement in the ground surface layer of 18Cr-8Ni austenitic stainless steel in order to clarify the characteristics of ground surface layer and examine the accuracy of stress measurement. The results obtained are as follows:
(1) The distribution of micro-strain formed in the ground surface layer corresponds to the changes of hardness and half-value breadth of diffracted X-ray profile in each layer. The depth of the strained layer increases with the increase of the downfeed of grinding, and that in dry grinding is larger than wet grinding.
(2) During the grinding of this testing material, the strain-induced transformation γ→α hardly takes place, because the surface temperature of workpiece rises.
(3) A high tensile residual stress reaching from 60 to 70kg/mm2 appears in the ground surface which has been ground severer than the condition of downfeed of 0.005mm by wet grinding in this experiment. And in the grinding of 18-8 stainless steel, thermal stress acts effectively to characterize the form of residual stress distribution.
(4) Using the constant ψ0 method with oscillation technique by an X-ray diffraction stress analyzer, the residual stress in the ground surface layer of 18-8 stainless steel can be measured accurately. However, the surface residual stress value obtained has to be corrected somewhat owing to the K-value used for stress calculation, the steep stress gradient and the roughness of ground surface.