Shear Fracture Criterion of Advanced High-Strength Steel Based on Stress Triaxiality and Equivalent Strain

Abstract

Advanced High Strength Steel (AHSS) are increasingly used in the automotive industry due to its higher strength and lower weight. The traditional forming limit criterion cannot accurately predict the unique shear fracture of AHSS, so great efforts have been made to develop failure criteria that can predict shear fracture. In this paper, a series of tensile and shear tests for four steel sheets of AHSS are designed, the stress triaxiality and equivalent strain are measured and solved, and the correlation between them and the performance parameters of steel sheets K and n is studied. In order to study the relationship between stress triaxiality and equivalent strain in the range of low stress triaxiality, the Hill'48 orthotropic model and MMC fracture model were used to establish tensile and shear fracture models of four dual-phase steels. Simulate and study the plastic fracture of AHSS. Solving the relevant parameters enriches the stress triaxiality of the four steel types, and establishes the relationship between the stress triaxiality and the equivalent strain, and verifies its correctness through tensile and bending tests and simulations. The results show that MMC can accurately predict the fracture of these four dual-phase steels, and the quantitative relationship between stress triaxiality and equivalent strain of the four dual-phase steels in the low-stress triaxiality range 0-0.3 is similar, which can be established and expressed by the performance parameters of each steel type.

A Review of Sheet Metal Forming Evaluation of Advanced High-Strength Steels (AHSS)

“…Figure 12 presents the methodology followed by the authors to calibrate material and fracture parameters based on experimental tests. Although the knowledge of the strain to fracture is the main ingredient of damage models [180], they used a phenomenological model to characterize the onset of damage; the crack initiation strain, rather than the fracture strain. Currently, most material characterization methods are based on the assumption of proportional loading histories.…”

Research on Forming Limit Stress Diagram of Advanced High Strength Dual-Phase Steel Sheets

“…Another typical problem that occurs during stamping of AHSS is the shear fracture [ 2 , 3 ]. Fu Q T et al [ 4 ] investigated the strength coefficient K , hardening index n , and stress triaxiality associated with this shear fracture.…”