The effect of strain rate sensitivity on theoretical prediction of limiting draw ratio for cylindrical cup drawing process

The plastic instability of cup drawing is usually measured by the limiting drawing ratio (LDR). A new and practically applicable equation for estimating the LDR in the cup (cylindrical) drawing with a flat nosed punch using process parameters namely yield strength (σy), strain hardening exponent (n), strain rate sensitivity (m), normal anisotropy value (image), friction coefficient (μ), radius of die arc (rd) and half die opening (r1), has been derived using an integral technique based on the load maximum principle for localization of plastic flow. The results shows that there is an interaction between the process parameters and the LDR and it is thereby possible to better understand and control cup drawing behavior for optimum press drawability. It is observed that there is an increase in LDR value as the strain rate sensitivity (m) increases.