Finite Element Implementation of a Temperature-Dependent Cyclic Plastic Model for SA508-3 Steel

Abstract

A new temperature-dependent cyclic plastic model, combining the nonlinear cyclic softening and kinematic hardening rules is established for a nuclear material of SA508-3 steel. A modified isotropic hardening rule is proposed to capture the temperature-dependent cyclic softening, and a modified kinematic hardening rule is established to improve the prediction of the ratcheting behavior by introducing an exponential function related to the accumulated plastic strain. The stress is updated by the radial return mapping algorithm based on the backward Euler integration. A new expression of consistent tangent modulus for the equilibrium iteration is derived, and then the proposed model is implemented into the finite element software ABAQUS by using the user material subroutine (UMAT) to simulate the temperature-dependent ratcheting behaviors of SA508-3 steel. Finally, the ratcheting evolutions of notched bars at elevated temperature are obtained by uniaxial stress-controlled cyclic tests, and the nonuniform strain fields on the surface of plates with a center hole is measured by using the digital image correlation (DIC) technology. Comparisons between experimental and simulated results of a material point and structural examples show that the implemented model can provide reasonable predictions for ratcheting behaviors and nonuniform strain fields of structures at different temperatures for SA508-3 steel.

Implementation of ABAQUS User Subroutines for Viscoplasticity of 316 Stainless Steel and Zircaloy-4

“…Chaboche and Rousselier [21,22] succeeded in modeling the rate-dependent mechanical behavior of 316 Stainless Steel based on a unified viscoplastic model including a nonlinear isotropic hardening rule, nonlinear kinematic hardening rule, and viscosity equation in the form of the power function. Since then, this model has been widely used to model the nonlinear mechanical behavior of metals and polymers, and it is called the Chaboche model [23][24][25][26][27]. Unlike 316 Stainless Steel, several experimental studies have been carried out to show that Zircaloy-4 has anisotropic viscoplastic properties due to its microstructural texture [28][29][30][31][32], and that Zircaloy-4 has a more complex kinematic hardening behavior.…”

Cyclic Creep Behavior and Modified Life Prediction of Bainite 2.25Cr-1Mo Steel at 455 °C

“…The strain accumulation for cyclic creep is usually time-dependent which is similar to ratcheting [8,9]. The ratcheting strain rate can be greatly influenced by a series of test parameters such as stress amplitude, stress ratio, and duration under hold stress.…”

Damage-coupled ratcheting behaviors of SA508 Gr.3 steel at room and elevated temperatures: Experiments and simulations

“…However, there are few literatures paying attention to the ratcheting behaviors of SA508 Gr.3 steel. In our previous work, some ratcheting experiments on the material and simple structure of SA508 Gr.3 steel were performed, and a modified cyclic plastic constitutive model was proposed to predict the ratcheting behaviors within limited cycles (Tian etal., 2018, 2017). But the influence of fatigue damage on the ratcheting response was neglected, so that it could not provide reasonable prediction for the whole-life ratcheting response.…”