Stress Measurement by Oscillation Technique of X-Ray Optical System

Abstract

In order to make X-ray measurement of stress using oscillation technique, its optimum conditions were studied with respect to the grain size of the specimen and the geometrical conditions of the soller slit system. Investigation was also made of the influence that the oscillating angle, the oscillating speed and the time constant would have on the diffraction profiles or the stress determined by X-rays.
The abnormality of diffraction profile of coarse grained specimen, caused by the geometrical conditions of the soller slit system, decreased by the oscillation of the X-ray optical system. And the number of grains, which contributed to the diffraction, increased by the oscillation technique. The diffraction profile obtained with the instrument became normal, when the range of oscillating angle was twice as large as the half breadth of the diffraction profile. And the peak position of diffraction profile could also be determined with ease.
The periodic change of intensity was observed on the diffraction profile when the oscillation technique was used. This phenomenon was remarkable with the increase of incident angle ψ₀. It was due to the difference of diffracted X-ray intensity for different angle in oscillation. When smaller oscillating angle than ±15°was chosen, however, the periodic change in intensity of the diffraction profile was kept sufficiently small under the time constant 8 or 16sec. which was what is generally used.
The analytical results showed that the value of cosecθ obtained from the oscillation technique was not exactly proportional to that of sin²ψ. But the experimental results showed that the cosecθ-sin²ψ relations obtained in the oscillating condition became approximately linear. The stress value of Fe {211} determined by conventional sin²ψ method using the data of ±10° oscillating condition, appeared to be 4∼6% smaller than that obtained from the data of fixed condition. Sin²ψ method seems to be practically useful to determine the stress, even when the oscillation technique is adopted, supposing that the oscillating angle is not so large and the stress of the specimen is not so high.