Revisit on Calculation Method of Cumulative Total Strain by Reversing Dynamic Load+Non Reversing Dynamic Load

In this paper, a damage evaluation method against reversing dynamic load (RDL) and “combination load of reversing dynamic load with non-reversing dynamic load” based on elastic-plastic analysis was examined using the ASME CC N-900) [1] for carbon steel and stainless steel piping elbows. First, the calculation method for equivalent total strain amplitude for fatigue evaluation of elbows was studied using elastic-plastic analysis of elbows for the results of static fatigue tests reported in the NUPEC Piping System Ultimate Strength Test Program Report [2]. In the elastic-plastic analysis of the elbow, a hybrid element model consisting of beam elements and shell elements was used, and the Chaboche model/kinematic hardening model was used to simulate the cyclic hardening behavior. The result shows that it is possible to simulate the static fatigue test results of elbows by the calculation method for equivalent total strain amplitude by proposed elastic-plastic analysis method. Next, since the calculation method for cumulative total strain for RDL and NRDL in this code case is a conservative method, we investigated alternative calculation methods for cumulative total strain. We could develop the elastic-plastic analysis conditions and calculation methods that can simulate cumulative total strain for carbon steel elbows.