Elastic-Plastic Fracture Mechanics Analysis of Cast Stainless Steel Pipes (Comparison of Z-Factor, Two-Parameter and J-T Methods)

Abstract

Since the ductility of cast austenitic stainless steel pipes decreases due to thermal aging embrittlement after long term operation, not only plastic collapse failure but also unstable ductile crack propagation (elastic-plastic failure) should be taken into account for the structural integrity assessment of a cracked pipe. There are mainly three procedures to obtain the elastic-plastic failure load; Z-factor, two-parameter and J-T methods. In this study, the difference in the failure load derived using these three methods was compared. The same material properties and J-integral solutions were used in order to investigate the influence of each analytical procedure. It was shown that failure loads obtained by the two-parameter method was more conservative than those obtained by the J-T method. An optimized failure assessment curve (FAC) was obtained for aged cast austenitic stainless steel. The reference stress method was also suitable for evaluating the FAC. It was concluded that the difference in the failure load obtained by the three methods was small enough from the viewpoit of engineering.