Hole expansion simulation considering the differential hardening of a sheet metal
Keywords:
sheet metal forming, hole expansion, finite element analysis, low carbon steel sheet, anisotropy, yield function, differential hardeningAbstract
The effects of material models on the predictive accuracy of the finite element analyses of hole expansion forming are investigated. The test material used is a zinc-coated low carbon steel sheet. Biaxial tensile tests of the test material are performed using cruciform specimens and the multiaxial tube expansion test method to determine proper material models for the test material. The material models used in the FEA are the isotropic hardening (IH) models based on the von Mises, Hill’s quadratic, and the Yld2000-2d (Barlat, et al., 2003) yield functions, in addition to the differential hardening (DH) model based on the Yld2000-2d yield function (Yld2000- 2d (DH)). The Yld2000-2d (DH) yield function gives the most accurate description of the biaxial deformation behavior of the test material. However, even the Yld2000-2d (DH) yield function could not accurately reproduce a tendency of the thickness strain ( p z ? ) distribution in the vicinity of the hole edge. It is concluded that a material model that accurately reproduces the anisotropic deformation behavior of the test material for a stress range from uniaxial tension to plane strain tension along the RD, 45°, and TD should be used in the FEA to improve the predictive accuracy for the p z ? distribution in the vicinity of the hole edge.
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