Effect of damage evaluation method and cyclic hardening models on strain-based fatigue assessment to a piping system under seismic loads

In this paper, strain-based damage assessment based on elastic-plastic FE analysis was carried out for the piping system test under seismic loads conducted at Bhabha Atomic Research Center (BARC, India) to suggest relevant damage evlaution method and cyclic hardening model. For the damage evaluation method, the cumulative plastic damage and cumulative fatigue damage assessment methods, suggested in ASME B&PV Sec. VIII and Sec. III, respectively, were considered. For the FE analysis, hybrid models consisting of the beam and solid elements were used, validated by comparing with the results using full solid models. To simulate the cyclic hardening behavior of the material, the bi-linear kinematic hardening model suggested in the JSME Code case and the Chaboche kinematic hardening model were considered. By comparing with test results, it is shown that predicted failure cycles are about 33–C;53 % of the test result, and the use of the cumulative plastic damage method is found to be more conservative than the cumulative fatigue damage method. The effect of the hardening model on evaluation results is found to be not so significant.