Evaluation of high strength steels fracture based on uniaxial stress-strain curves

Abstract

Predicting the ultimate capacity of components made of high strength steel (HSS) is a numerically challenging task. The fracture performance of HSS from different steel grades, producers, and manufacturing processes (rolling, cold forming, etc.) varies greatly. It is costly to conduct a series of experiments for each typical HSS structural component to identify the parameters of the fracture model. An attempt is made to evaluate the fracture material properties based only on the standardized uniaxial stress-strain curve. The uncoupled fracture model was implemented through a user subroutine VUMAT (ABAQUS) to evaluate the ductile fracture of HSS, where a rate-independent non-linear isotropic J2 hardening model is used in combination with a separate Hosford-Coulomb fracture model. The detailed procedure to identify the material parameters based on only the uniaxial stress-strain curve of steel grades S700 and S960 are provided for the sake of illustration of possible applications. The proposed fracture model and identified parameters are validated based on the experimental results of the HSS plate with different hole sizes in the middle of the dog bone specimens. Besides, a desktop study of a single K gap joint with β = 0.5 made of square hollow sections using S700 and S960 is used to illustrate a possible application of the fracture model in a simplified model of the structural joint.