Strain-Based Low-Cycle Fatigue Assessment on Piping Elbow

Abstract

In this paper, a strain-based damage evaluation method based on elastic-plastic analysis was examined for carbon steel piping elbows. In order to simulate the results of the fatigue tests on piping elbows reported in the ‘NUPEC Piping System Ultimate Strength Test Program Report’, we carried out the strain-based damage evaluation by using elastic-plastic analysis. In the elastic-plastic analysis of the elbows, a hybrid model consisting of beam elements and shell elements was used, and the Chaboche model was used to accurately simulate the cyclic hardening behavior of the material. The fatigue curve used for fatigue damage evaluation was the fatigue curve by ‘modified Manson universal slope method’. As a result, it was confirmed that the fatigue test results of piping elbows reported in previous studies could be simulated using elastic-plastic analysis by using elastic-plastic analysis and the ‘correction method for fatigue life based on the ductile consumption law’. In addition, we also report on our investigation into the ‘cumulative strain estimation method’ used in the ‘cumulative plastic damage evaluation for combination load of reversing dynamic load and non-reversing dynamic load’ in the ASME code case (CC N-900).