Fracture prediction and damage evolution of Q690 HSS under various stress states

Abstract

The high strength and light weight of the high strength steel (HSS) make it extensively used. However, the reduction in ductility often leads to prominent fracture issues. The Q690 steel, with a yield strength greater than 690 MPa, is one type of Chinese HSS, and its fracture behavior, especially under complex stress states, is a growing concern. Therefore, this study tests a series of monotonic tensile specimens of Q690 HSS with various stress states to obtain the fracture results. Subsequently, a new Lode-dependent enhanced Lemaitre (NLEL) model is proposed. This model integrates the damage effect of the Lode parameter into the original Lemaitre model, enhancing the accuracy of fracture prediction specifically under shear-dominated stress scenarios. Comparative analysis among the Lemaitre model, NLEL model, and another Lode-dependent enhanced Lemaitre (LEL) model reveals that the proposed NLEL model delivers more comprehensive fracture prediction across all tested specimens, including smooth round bars, notched round bar, flat grooved plates, pure-shear plates as well as tensile-shear plates. Furthermore, this study delves into the analysis of damage evolution under representative stress states and initiates discussions regarding the coupled damage model.