Numerical failure analysis of a stretch-bending test on dual-phase steel sheets using a phenomenological fracture model

Abstract

a b s t r a c tAdvanced High Strength Steels (AHSS) are increasingly used in automotive industry due to their superior strength and substantial weight advantage. However, their compromised ductility gives rise to numerous manufacturing issues. One of them is the so-called 'shear fracture' often observed on tight radii during stamping processes. Since traditional approaches, such as the Forming Limit Diagram (FLD), are unable to predict this type of fractures, great efforts have been made to develop failure criteria that could predict shear fractures. In this paper, a recently developed Modified Mohr-Coulomb (MMC) ductile fracture criterion (Bai and Wierzbicki, 2010) is adopted to analyze the failure behavior of a Dual Phase (DP) steel sheet during stretch-bending operations. The plasticity and ductile fracture of the present sheet are fully characterized by a Hill'48 orthotropic model and a MMC fracture model, respectively. Finite element models with three different element types (3D, shell and plane strain) were built for a Stretch Forming Simulator (SFS) test (Shih and Shi, 2008), numerical simulations with four different R/t values (die radius normalized by sheet thickness) were performed. It has been shown that the 3D and shell element simulations can predict failure location/mode, the upper die load-displacement responses as well as wall stress and wrap angle at the onset of fracture for all R/t values with good accuracy. Furthermore, a series of parametric studies were conducted on the 3D element model, and the effect of tension level (clamping distance), tooling friction, mesh size and fracture locus on failure modes and load-displacement responses were investigated.

The Sandia Fracture Challenge: blind round robin predictions of ductile tearing

“…In the special case where c 1 = 0 and c 3 = 1, the model reduces to the maximum shear stress criterion. To fully exploit the accuracy and predictive power of the MMC model, dense experimental programs covering a wide range of stress states are recommended, such as the ones shown in Beese et al (2010) and Luo and Wierzbicki (2010). In addition, MIT team makes use of the inverse calibration (or so-called hybrid experimental-numerical) procedure that requires FE simulation of each test.…”

Development of Three Dimensional Fracture Strain Surface in Average Stress Triaxiaility and Average Normalized Lode Parameter Domain for Arctic High Tensile Steel: Part I Theoretical Background and Experimental Studies

“…(Bao and Wierzbicki, 2004;Bao, 2005;Choung et al, 2012;Choung and Nam, 2013;Choung et al, 2014a;Choung et al, 2014b). (Bai and Wierzbicki, 2008;Luo and Wierzbicki, 2010;Lou et al, 2012;Bai and Wierzbicki, 2010;Dunand and Mohr, 2011;Lou and Huh, 2013). Table 1 Chemical components of EH36.…”

Failure characteristics of a dual-phase steel sheet

“…Mirone and Corallo (2010) used the maximum shear stress criterion, the Bao and Wierzbicki (2004) criterion and an evolution of the later criterion by Wierzbicki et al (2005) to study the influence of both the stress triaxiality and the Lode parameter on fracture in four different metals. Luo and Wierzbicki (2010) predict shear fracture during the stretch-bending of dual-phase steel using the MMC criterion. The special case of shear fracture, due to the high-curvature die radii, in sheet forming operations of three dual-phase steels was studied by Kim et al (2011).…”