Influence of Triaxiality Factor on Low-Cycle Fatigue of Pipe Fittings

Abstract In 2019, ASME Section III and JSME published a code case (ASME CC N-900[1]/JSME NC1 CC-008[2]) regarding seismic design codes for piping by using elastic-plastic analysis. As shown in PVP2023-107170[3] “Seismic Design Method of Crossover Piping Across Building Isolation Boundary”, while it would be clear that this code case using elastic-plastic analysis allows for a reasonable seismic design of the piping, there are few examples of actual seismic design works by using this code case because of its conservatism on applicability limitations such as fabrication strain limitations, strain base criteria using triaxiality factor [TF], and calculation method of applied strain. Therefore, we have discussed the technical issues to be addressed to revise ASME CC N-900 for actual piping design use. In this paper, we proposed the revisit results on allowable strain amplitude without [TF] against Reversing Dynamic Load (RDL), based on low-cycle fatigue testing and past studies on piping failure mode by Reversing Dynamic Load (RDL).