Finite-Element Simulation of Deformation and Breakage in Sheet Metal Forming : 1st Report, Basic Theory

Abstract

In the analysis of sheet metal forming, the constitutive equations are examined with respect to prediction of breakage strains. Breakage initiation is numerically evaluated by the method proposed previously by one of the authors (Gotoh) in which the onset of localized necking is adopted as the breakage condition. Numerical results of limiting strains evaluated by the use of the J 2-Gotoh's corner (J2G) theory and biquadratic anisotropic yield function are in good agreement with experimental results. Next, the commercial FEM code 'JNIKE3D' is improved by introducing them. The evaluation function for breakage is also introduced into the code. A modified radial return method is proposed and adopted as the stress-point integration algorithm for this anisotropic case. As an example, a necking in tensile test is simulated to verify the effectiveness of the improved JNIKE3D.