Abstract
Thermal fatigue crack extension test had been conducted on cylindrical specimens of rotor casing material. Each specimen was initially notched circumferentially either circularly or half-elliptically along the inside surface, and subject repeatedly to thermal stress caused by sudden water-cooling on its inner surface after electric furnace heating. Test results show that the crack depth extension rate was decreased for larger notch depth and the specimens with circular notch show larger crack extension than those with half elliptical notch. Transient thermal and stress state of the specimen was analyzed by axi-symmetric FEM, and the numerical stress distribution was used to calculate the stress intensity factor and to perform crack extension analysis. For small circular notch, the elasto-plastic FEM analysis resulted better agreement with the experimental crack depth extension and Meshii's elastic method showed conservative estimation. For the half-elliptical notch, CRIEPI's influential function method showed good correlation with experimental results.
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