抄録
The Committee for X-ray Study on Deformation and Fracture of Solid realized the necessity of having full grasp of the level of industrial development and dissemination of the technique for measuring residual stress by application of X-ray radiation. So it was decided to circulate the same specimen round many places, and study the accuracy and variance of the measured values of residual stress. To trace the cause of variance in the results and to improve the measuring technique, three joint studies were conducted from 1966 to 1970 and the results have been compared and discussed. Hereunder is given the outline of the joint studies.
The 1st joint study was carried out on a carbon steel disc with a diffraction ring of sharp width. In this series of tests both the photograph method and the counter method were adopted for comparison. The difference in the measured values between the irradiations of CoKα rays and CrKα rays were checked.
The 2nd joint study was carried out on a heat-treated carbon steel specimen with a broad diffraction ring. The counter method with CrKα rays was used. The major object of the study was to investigate the variance in the measured values.
The 3rd joint study was carried out on the cylindrical surface of a bearing steel with a broader diffraction ring than that of the 2nd round specimen. The target conditions were specified in order to maintain the measuring conditions as constant as possible.
It is found from these joint studies that there is larger variance in the values measured by the photograph method than those measured by the counter method. The factor has been confirmed to lie in the photography technique in the photograph method of X-ray stress measurent. When the counter method is used, the values measured with the same specimen show a deviation of about ±5∼±10kg/mm2 from the mean value, though with some exception. The wider variance observed in the exceptional cases can be attributed to technical errors in the focussing, inadequate maintenance of instruments, personal errors in measurement and irregularities in the handling conditions.
It is necessary to get hold of the factor for the variance in the measurement, for the X-ray technique of stress measurement is expected to be most effective in the research of the strength of materials as well as in the practical application. The Division of X-Ray Stress and Strain Measurement has scheduled to continue their studies to clarify the factors causing the variance.
