ホールドリル法による実機残留応力測定技術の開発

（外部応力負荷による測定精度の検証）

抄録

Stress corrosion cracking in nuclear power plants can be prevented by the shot peening process which gives compressive residual stress to the surface of components. Therefore, it is important to evaluate the residual stress distribution near the surface of the components. However, it is concerned that the residual stress induced by the peening may decrease during long term operation. For this reason, it is necessary to know the actual residual stress distribution after long term operation. After the East Japan Earthquake, several nuclear plants were decided to be decommissioned. By measuring the residual stress on the decommissioning components, it is possible to evaluate the change in the effect of the peening due to the long term operation. There are some techniques to measure the residual stress. Hole drilling method is relatively simple and inexpensive, and can also measure the residual stress distribution in depth. However, the accuracy of the hole drilling method has not been understood yet, particularly near the surface region. In this study, the accuracy of the hole drilling method was investigated by the bending tests where the applied load was identified accurately. It could be assumed that the stress distribution by the bending test has a linear distribution. As a result, the stress distribution produced by the bending test agreed with the stress distribution measured by the hole drilling method. However, the accuracy of the measurement could not be always confirmed near the surface, which suggested that further verification would be necessary.