SA-06-1(111) Enhanced Reference Stress Approach for Defect Assessment of Components Operating at High Temperatures(Flaw Assessment at Elevated Temperature 1)

概要

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For assessing significance of a defect in a component operating at elevated temperatures, engineering estimation of the creep fracture mechanics parameter, C^*-integral, is essential. Although the J estimation equation in the GE/EPRI handbook can be used to estimate the C^*-integral when the creep-deformation behavior can be characterized by the power law creep, such power law creep behavior is a very poor approximation for typical creep behaviors of most materials. Accordingly there can be a significant error in C^*. To overcome problems associated with GE/EPRI approach, the reference stress approach has been proposed, but the results can be sometimes unduly conservative. In this paper a new method to estimate the C^*-integral for defective components is proposed, which improves the accuracy of the reference stress approach significantly. The proposed calculations are then validated against elastic-creep finite element (FE) analyses for four different cracked geometries following various creep-deformation constitutive laws. Comparison of the FE C^* values with those calculated from the proposed method shows good agreements. Furthermore, the proposed method can be also used to estimate the elastic-plastic J-integral for assessing significance of the defect against the short-term failure. Therefore, the proposed method is valuable for defect assessment of components operating at high temperatures.
一般社団法人日本機械学会の論文
2001-06-03