On the Permissible Fluid-Pressure Path in Hydroforming Deep Drawing Processes—Analysis of Failures and Experiments

The geometrical and material constraints which limit the quality of hydroforming products in regard to failure by wrinkling (buckling) and/or rupture (tensile instability) are investigated in a unified framework. The analysis is based on limit theorems of plasticity (with a power-law hardening and Mises-Hill normal anisotropy) and resulted in distinct bounds for the permissible operating fluid pressure path. The parameteric study which follows includes a wide range of physical variables, some of which (not considered hitherto) show substantial effects on anticipated failure. Experiments with copper, aluminum, steel, and stainless steel agree very well with the supposition that premature failure (up to certain situations) is avoidable if the fluid pressure path is restricted to travel only within the suggested bounds.