Effect of alternating blank holder motion of drawing and wrinkle elimination on deep-drawability

The effect of controlling blank holder motion by a newly proposed algorithm on deep-drawability was investigated for a circular-cup deep-drawing process of a thin sheet metal, from the perspective of wrinkle behavior as well as the fracture limit. The algorithm for controlling blank holder motion, such that blank holder force is extremely low, by temporarily allowing wrinkling has been proposed by the authors for improving the deep-drawability of thin blanks. Experimental deep drawing tests of a Cu alloy sheet were carried out to evaluate the effect of motion control on wrinkle behavior. Finite element (FE) simulations of the deep drawing process were also conducted to investigate the effect of the method on fracture damage reduction. In the previous work by FE simulation, we showed that the motion control method is effective for forming relatively thin sheet blanks, and that the performance of the control method significantly depends on control parameters, i.e., minimum and maximum allowable wrinkle heights, which are associated with wrinkle recognition. The results of the experiment indicated that wrinkle elimination can be successful if wrinkles are within the allowable height range. FE simulation results also indicated that deep-drawability can be improved as a result of the reduction of ductile damage accumulation when using blank holder control.