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Abstract
As a flexible‐die forming process, viscous pressure forming (VPF), which uses a kind of semisolid, flowable and viscous material as pressure‐carrying medium, offers a simple and versatile approach to low volume stamping of difficult‐to‐form sheet metal alloys. As a result of the relatively low flowability of viscous medium compared with fluid, the deformation sequence of the workpiece can be controlled and regulated through controlling the loading mode of viscous medium. In the present study, viscous pressure bulge (VPB) tests with three kinds of loading location of viscous medium (central zone, corner zone and the whole deformation zone) and three loading velocities were conducted to investigate the effects of loading mode on sheet formability. Experimental results show that increasing loading velocity reduces sheet formability in viscous pressure bulge tests with conventional loading location and changing the loading location of viscous medium can greatly affect sheet formability. Numerical simulations were performed to reveal the reason why changing the loading location affects sheet formability. It is found that nonuniform pressure distribution is the main reason why loading location affects sheet formability. The pressure distributions for the condition of injecting viscous medium at the die corner zone are beneficial to improve the formability of sheet metal.
The authors would like to acknowledge the financial support of project No. 50805034 from the National Science Foundation of China (NSFC) and project No. 20100471028 from the postdoctoral foundation of China.