A blank holding method to avoid wrinkle and fracture in press forming process for sound diaphragm with ultra-thin copper sheet: Experiment and FE simulation

초록

This study focuses on a method to avoid wrinkle and fracture during press forming of an ultra-thin copper sheet for the sound diaphragm. Because the ultra-thin copper sheet experiences both wrinkle and fracture even with controlling the blank holding force, a polyethylene pad was employed to obtain successful forming results without the wrinkle and the fracture. Experiments and FE simulations of the press forming were conducted to evaluate effects of the lubrication and the pad utilization with different blank holding forces. Simulation results reveal that the stress and the strain fields become more uniform resulting both wrinkle and fracture would be avoided during the forming with the pad. In addition, the pad affects reduction of the stress concentration on the holding region so that the amounts of the wrinkle are significantly reduced. The pad technique might be widely used for forming of ultra-thin materials to prevent wrinkle and fracture simultaneously.

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