Effect of Anisotropic Yield Functions on the Accuracy of Hole Expansion Simulations for 590 MPa Grade Steel Sheet

Abstract

The deformation behavior of a high-strength steel alloy with a tensile strength of 590 MPa is investigated both experimentally and analytically to clarify the effect of the material model (anisotropic yield function) on the predictive accuracy of the finite element simulation of hole expansion. Biaxial tensile tests of the test material have been carried out. Measured contours of plastic work and the directions of plastic strain rates are found to be in good agreement with those predicted using the Y1d2000-2d yield function with an exponent of 6. The anisotropy in uniaxial tensile flow stresses and r-values has been also in good agreement with those predicted by the Y1d2000-2d yield function, as opposed to the previous study [T.Kuwabara, K.Hashimoto, E.Iizuka and J.-W.Yoon: J. Jpn. Soc. Technol. Plast., 50 (2009), 925]. Forming simulations of and experiments on the hole expansion of the test material have been carried out using the von Mises, Hill's quadratic and the Y1d2000-2d yield functions with different exponents. The Y1d2000-2d yield functions have given the closest agreement with the experimental results. Consequently, it is found that anisotropic yield functions significantly affect the predictive accuracy of the deformation behavior of an anisotropic sheet metal subjected to hole expansion and that the biaxial tensile test is effective in identifying a proper anisotropic yield function to be used in the hole expansion simulation.