A New Equation of Load Curve of Critical Wrinkles Variable Blank Holder Force in the Warm Deep-Drawing of Twin-Roll Cast Mg Sheets

摘要

A new equation of load curve of critical wrinkles variable blank holder force (VBHF) during the warm deep-drawing of twin-roll cast Mg sheets was derived, which based on correlative energy conservation theorem. Experiments of limited drawing ratio (LDR) suggested that calculated load curve of minimum wrinkles using the new formulas fit to the tested data very well. The LDR was improved from 1.75 to 1.92 by using a new three segments way of load VBHF applied in the warm deep-drawing, at the forming temperature of 523 K and punch velocity of 45 mm/min. Finally, the VBHF warm deep-drawing process is also simulated by the finite element method, and a new technique of variable punch velocity (VPV) is applied in the simulation. The simulation indicated that the VPV technology can improve the LDR from 1.86 to 2.26 and gain the whole cylinder part, at the forming temperature of 523 K, when the punch velocity varied gradually from 30 to 5 mm/s.