Modeling mechanical properties of 21-Cr ferritic stainless steel with variation of stress ratio

摘要

A phenomenological material model describing anisotropic plastic behavior of 21-Cr ferritic stainless steel sheet was investigated using a non-quadratic anisotropic yield function. Uniaxial tension tests in rolling, diagonal and transverse directions, equi-biaxial bulge test and disk compression test were conducted for determining parameters of the yield criterion. Especially, R_b(ε_(TD) /ε_(RD)) values obtained from disk compression test and equi-biaxial bulge test were compared. For modeling of yield anisotropy of a metal sheet, the yield function, Yld2000-2d has been widely used by assuming that the shape of its initial yield locus does not change during deformation. In this study, in order to consider variation of stress ratios, coefficients (α1～α8) of Yld2000-2d model were assumed to be functions of the equivalent plastic strain and the corresponding yield function was implemented into the user material subroutine in the FE software ABAQUS. Effects of variation of stress ratios during deformation were studied using single element FE simulations. Results showed that Yld2000-2d model with varying coefficients could describe the stress-strain curves under both uniaxial tension and equi-biaxial bulge better than that with constant coefficients.