圧縮力を駆動力とした金属薄板の張出し加工において工具形状が成形性に及ぼす影響

抄録

This paper presents a stretch forming method that applies compressive force. A deep cup with a flange could be formed in only one process by using this proposed method, because the forming limit of the metal improves in compressive stress field. In this method, tools are a punch and a die with a hole, and the main parameters are the depth of the die hole and the clearance between the punch and the die. Optimum parameters were investigated for producing deep cups without defects by the finite element method (FEM) and experiments. As a result of FEM, when the clearance c was too large or the die hole depth d_dh was too small compared to the initial blank thickness t₀, the material flow could not be controlled appropriately, and then the side wall of the cup curved. A deep cup without defects could be obtained by setting the clearance c to 0.25 t₀-0.5 t₀ and setting the die hole depth d_dh to 0.75 t₀-1.0t₀. In experiments, a deep cup which aspect ratio is 0.83 was formed successfully under the optimum condition. This method would enhance the productivity and reduce manufacturing cost for forming deep cups with the flange.