破壊評価線図を用いた構造健全性評価における部分安全係数の感度解析

概要

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The partial safety factor (PSF) method with failure assessment diagram (FAD) is incorporated in fitness-for-service (FFS) guidelines such as API579 and SINTAP because it can evaluate crack-like flaws in service quantitatively and easily. Although API579 leaves the variance of yield stress out of consideration, it effects on PSF for strength of materials such as stainless steels, which have strong ductility. In addition, PSFs vary according to the variance of parameters used in evaluation. In this paper, we have evaluated the effect of the variance of parameters, especially of the applied stress and yield stress, on structural reliability and PSFs. As a result, the PSFs used for the evaluation of crack-like flaws must be calculated for each variance of the applied stress. The same PSFs can he used for the evaluation regardless of the variance of the yield stress in the brittle fracture dominant region. On the other hand, in the plastic collapse dominant region, the PSFs must be calculated for each variance of the yield stress. If the variance of the yield stress is ignored, unallowable crack-like flaws can be mistaken as allowable.
2009-08-25