Micro-hydromechanical deep drawing of metal cups with hydraulic pressure effects

Abstract

Micro-metal products have recently enjoyed high demand. In addition, metal microforming has drawn increasing attention due to its net-forming capability, batch manufacturing potential, high product quality, and relatively low equipment cost. Micro-hydromechanical deep drawing (MHDD), a typical microforming method, has been developed to take advantage of hydraulic force. With reduced dimensions, the hydraulic pressure development changes; accordingly, the lubrication condition changes from the macroscale to the microscale. A Voronoi-based finite element model is proposed in this paper to consider the change in lubrication in MHDD according to open and closed lubricant pocket theory. Simulation results agree with experimental results concerning drawing force. Changes in friction significantly affect the drawing process and the drawn cups. Moreover, defined wrinkle indexes have been shown to have a complex relationship with hydraulic pressure. High hydraulic pressure can increase the maximum drawing ratio (drawn cup height), whereas the surface finish represented by the wear is not linearly dependent on the hydraulic pressure due to the wrinkles.

Keywords

micro-hydromechanical deep drawing / microforming / size effects / lubrication / Voronoi

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Acknowledgements

The first author is grateful for the financial support given by the Chinese Scholarship Council (CSC 201206160011) and for the international postgraduate tuition award offered by the University of Wollongong. The authors would also like to thank the Australian Research Council for their financial support. This study was also supported by the invitation fellowship program of the Japan Society for the Promotion of Science (Z. Y. Jiang).

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