Ductile Fracture Investigation of High-Strength Steel SM570 under Low Stress Triaxiality

Abstract

A comprehensive understanding of the fracture behavior of high-strength steel is of great significance for its structural application. In this study, experiments were conducted to investigate the ductile fracture mechanism of high-strength steel SM570, one type of conventional structural steel. Two types of shear specimens, one with symmetrical notches and the other with asymmetrical notches, were designed, and by changing the notch angles, a wide range of low-stress triaxiality could be obtained. Based on the discussion of the experimental results, crack initiation, and its propagation up to fracture failure were clarified. Compared with the fracture behavior of SM490 (one type of conventional normal-strength structural steel), the SM570 with higher yield stress has relatively severe stress concentration, the crack initiation appears earlier, and the brittle fracture is more likely to occur. Numerical simulations based on the finite element method (FEM) were performed with ABAQUS to obtain the stress triaxialities and equivalent plastic strain of the symmetrical and asymmetrical specimens. A modified N-VG model with a fracture criterion at a negative and low-stress triaxiality range from −0.6 to 1/3 was proposed for evaluating the fracture behavior of steel SM570.