Thickening of cup sidewall through sheet-bulk forming with controllable deformation zone

Buckling is one of the main challenges in thickening the sidewall of a deep drawn cup. To overcome this problem, a novel sheet-bulk forming method, upsetting with a controllable deformation zone, was developed in this study to prevent the buckling during sidewall thickening. In this method, the material from the protective cavity of the die is pushed into the forming cavity under a counter force to establish a stabilised deformation zone, which can eliminate the limitation of the initial slenderness ratio in conventional upsetting methods. The experimental and simulated results reveal that the occurrence of buckling can be successfully avoided through upsetting with a controllable deformation zone. The forming load tends to remain unchanged because of the existence of a stable deformation zone. Additionally, the forming quality can be improved, and a uniform distribution of hardness in the cross section can be obtained, thereby improving the performance-in-service.