Implications of a 'cross-rolled' yield surface approximation on deep drawing

摘要

During deep-drawing, two issues manifest themselves that are due to normal and planar anisotropy in the sheet. These are a dependence of the Limiting Draw Ratio (LDR) on the average thinning ratio (R-value), and a dependence of ear formation and thinning around the circumference on the variation of R-value in the plane of the sheet. The quadratic yield surface has been applied to these issues and it has been demonstrated that there are numerous higher exponent yield criteria that may more closely duplicate experimental trends. These predict varying degrees of R-value dependencies of uniaxial yields and strength ratios in multiaxial loading paths. The result of this is that there are sometimes subtle and sometimes substantial differences in the predictions of the various yield surfaces on deep drawing regarding LDR and earing.