Low-cycle fatigue behavior and damage mechanism of AH36 steel based on a continuum damage coupled unified elastoplastic model

Abstract

This paper aims to investigate the fatigue behavior and damage mechanism of AH36 steel under low-cycle fatigue (LCF) loading by a combined experimental and numerical approach. Systemic monotonic tensile and cyclic loading tests with different loading protocols are conducted to calibrate and determine the elastic and plastic model parameters, and to explore cyclic stress–strain response as well as LCF damage behavior. A continuum damage coupled unified elastoplastic model based on the continuum damage mechanics is proposed to describe the hysteresis behavior and fatigue characteristic of AH36 steel; meanwhile, a procedure is developed by the VUMAT subroutine in ABAQUS/Explicit to numerically evaluate the fatigue damage evolution and lifetime prediction throughout the whole fatigue process. Fatigue damage accumulation and stress redistribution within the structure are conducted to clarify damage initiation and evolution process until structural failure. Reasonably good agreement is achieved when comparing the cyclic stress–strain response and stress peak between experimental measurements and numerical simulation, and lifetime prediction indicates better accuracy with an average error of less than 10%.