Shunichi Takahashi

Application of Synchrotron Radiation to Residual Stress Analysis by IP/cosα Method

The X-ray stress measurement with synchrotron radiation (SR) and an image plate (IP) was conducted using the facility of the Photon Factory (PF) of the High Energy Accelerator Research Organization (KEK). The influence of 2θ on stress measurement with the cosα method was investigated. The experiments were conducted under the conditions of 2θ=170 deg, 156.4 deg and 127 deg respectively. It was found that the hypothesis on the relation between the accuracy and the diffraction angle in the X-ray method is not valid in case of the cosα method.

Residual Stress in Railway Rails by IP/cosα Method

In this study, a new portable X-ray stress analyzer was designed and manufactured. The purpose of its use is to evaluate the rolling contact fatigue damage in rails for establishing an effective rail maintenance method. An image plate was used in this analyzer for detecting diffracted X-ray beams. The cosα method was adopted for X-ray stress analysis from X-ray diffraction data. A fundamental experiment was made first for examning the present measurement system. Residual stresses in rails used in service for six years were also investigated in this study.

Influence of Peak Determination Method on Area Detector Type Neutron Stress Measurement

The influence of the peak determination method on the area detector type neutron stress measurement method was investigated. Two peak determination methods, the half value breadth method and the centroid method, were compared and discussed in this paper. Experiments and simulation studies were carried out respectively. The first experiment was conducted during the tensile stress test with a steel specimen having the thickness of 6mm, and the second experiment was conducted with steel specimens in the stress free state having the thickness between 1 mm to 20 mm. As a result of the experiments, it was found that the peak determination method has an affect on the area detector type neutron stress measurement. A numerical simulation study was also conducted and showed similar result as the experiments.

Application of Neutron Diffraction Technique to Industrial Materials

As an important industrial problem, the rolling contact fatigue damage is accumulated in rails during the repeated passage of trains over the rails, and rail failures may occur from the cracks grown in the rails. In order to prevent such rail failures, the estimation of the behavior of internal rail cracks is required based on the exact engineering analysis model as well as conducting rail test to search rail defects. The purposes of this paper are to apply the neutron stress measurement to rails, and to obtain residual stress state in the rails for the above purpose. The rail samples used were those that have been used in service line in Japan for about six years (222 million gross tons). The neutron measurement was conducted using the Residual Stress Analyzer (RESA) of the Japan Atomic Energy Agency (JAEA). The present measurement of stresses in rails by the neutron diffraction method was the first attempt in Japan.