| 摘要 |
A method of forming a workpiece, including the steps of: providing a center ram, a first outside ram, a second outside ram, and a die; pressing the center rain against the workpiece and toward the die to a first predetermined die depth; trapping the workpiece between the center ram and the die; pressing the first outside ram and the second outside ram against the workpiece and toward the die to a second predetermined die depth; and stretching the workpiece beyond a yield tensile strength of the workpiece material. The die surface has a die center surface which includes at least part of a first arcuate surface, a first planar surface, and at least part of a second arcuate surface. The center ram surface is complimentary in shape to the die center surface.
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