弾塑性有限要素解析によるき裂を有する構造物の耐荷重評価（ステンレス鋼平板および管の耐荷重予測方法の検討）

Abstract

A procedure for obtaining the load carrying capacity of cracked components of ductile material conducting by an elastic-plastic finite element analysis (FEA) was discussed. First, tensile tests using stainless steel plate specimens with through wall or part-through wall crack were performed. The deformation and strain were measured by the digital image correlation technique. Ductile crack initiation behavior was also observed. The tests was simulated by the elastic-plastic FEA. It was shown that the maximum load obtained by the FEA was about 1.15 times that obtained by the tests. The FEA using the stress-strain curve estimated by the K-fit method, in which the curve is estimated using the yield and ultimate strengths, agreed well that obtained using the curve by the tensile test. The FEA was also performed for simulating four point bending tests of cracked stainless steel pipes. Since the drop in applied load caused by ductile crack penetration of wall thickness was difficult to simulate, the stress penetration criterion was newly proposed. It was shown that the load for crack penetration could be predicted by the stress penetration criterion. Finally, the procedure for performing the FEA using the K-fit method and the stress penetration criterion was discussed for applying fitness-for-service assessments. The procedure allows deriving the load carrying capacity of cracked components which has a complex geometry or has inhomogeneous material properties such as welding portion.