A three-dimensional constitutive model of High Strength Structural steels

Abstract

Due to the sufficient toughness and high strength, the High Strength Structural (HSS) steels with nominal yield strength not less than 460 MPa are rapidly gaining popularity in steel construction worldwide. The failure point of steel elements in steel structures typically experiences significant plastic deformation at triaxial stress levels. In order to study the ultra-low cyclic behavior of HSS steels at various triaxial stress states, a series of cyclic tests on three typical HSS steels specimens with various initial geometrics are designed and conducted in the present study. The characteristics of HSS steels including Lode angle dependence of yield strength, combined hardening and three-stage strength softening are observed. Moreover, the strength softening laws of HSS steels are different at various stress states. However, the existing constitutive models fails to capture strength softening of HSS steels when subjected to a range of loading types in terms of various triaxial stress states. Based on ductile damage mechanism, a new cyclic constitutive model (HSS-3D) with consideration of damage accumulation and influence of triaxial stress states is proposed. The HSS-3D model is implemented into ABAQUS via user subroutine and its applicability to HSS steels is verified. The evolution and distribution of damage of HSS steels under various stress states are studied.