The whole-life ratcheting behavior of internal pressurized elbow subjected to force and displacement cycling with a damage-coupled kinematic hardening model

In this paper, a study was conducted on the ratcheting-fatigue tests of internal pressurized elbow in the primary circuit of nuclear power plant under force and displacement cycling, and the ratcheting effects at the critical locations of the elbow were evaluated. Based on thermodynamics and continuous damage mechanics theory, the damage evolution rule of the material was derived according to the derivative relationship between damage dissipation potential and damage related variable. A cyclic plastic constitutive model with damage was established by combining the damage evolution rule with Chen-Jiao-Kim (CJK) kinematic hardening rule. The subroutine of this constitutive model was embedded in ANSYS finite element software to numerically evaluate the evolution law of the whole-life ratcheting of the elbow. The results indicate that this damage-coupled kinematic hardening model can describe the whole-life ratcheting behavior of the elbow, and the numerical calculation results and experimental data are basically identical.