Numerical modeling for accurate prediction of strain localization in hole expansion of a steel sheet

• Published in: International journal of solids and structures 2019-01, Vol.156-157, p.107-118
• Main Authors: Lee, Jeong-Yeon, Lee, Ki-Jung, Lee, Myoung-Gyu, Kuwabara, Toshihiko, Barlat, Frédéric
• Format: Article
• Language: English
• Subjects: Anisotropic yield function; Anisotropy; Computer simulation; Crack initiation; Finite element analysis; Finite element method; Finite element simulation; Hole expansion; Low carbon steels; Material properties; Mathematical models; Metal sheets; Parameters; Plane strain; Plane stress; Plastic anisotropy; Plastic deformation; Sheet metal; Simulation; Steel; Strain localization; Strain rate; Three dimensional models; Yield strength
• ISSN: 0020-7683; 1879-2146
• DOI: 10.1016/j.ijsolstr.2018.08.005

•A numerical modeling approach to predict the localization behavior of sheet was investigated.•Plastic anisotropy of the sheet was taken into account using non-quadratic anisotropic yield functions.•Constitutive description exhibited a significant influence on the hole expansion formability even with slight change in the yield function parameters.•The computational accuracy was significantly improved when the yield function parameters were optimized based on flow stresses and plastic strain rate ratios. The hole expansion of a low carbon steel sheet shows an interesting feature that localized thinning and subsequent crack initiation are observed inside the specimen, and not at the hole edge as is typically expected. The present work investigated a numerical modeling approach to predict this localization behavior within the framework of a finite element (FE) analysis. Plastic anisotropy of the sheet was taken into account using the anisotropic yield functions Yld2000-2d and Yld2004-18p for the plane stress and three-dimensional elements, respectively. Careful examination of the FE model revealed that the influence of the out-of-plane stress is very small, suggesting that shell elements can be efficiently used in the analysis. The influence of friction was also found to be negligibly small. However, the constitutive description exhibited a significant influence in that even a slight change in the yield function parameters resulted in a considerable difference in the prediction. For this reason, several sets of parameters were obtained based on the different material properties, and their influences on the hole expansion simulation were analyzed. In particular, the prediction accuracy could be greatly improved when the yield function parameters were optimized such that the flow stresses and plastic strain rate ratios in uniaxial and plane strain states were well captured.