The TFC process (a) the first stroke (b) the second stroke As indicated in Fig. 2(a), the flap gaskets are installed on the anvil in the first stroke. The bottom ring is placed on the flap gaskets to ensure a certain depth of the bottom dies. The punch compresses the sheets. Initially, the sheets are subjected to forces within the elastic range, and sheets undergo elastic deformation. As the punch is gradually embedded in the upper sheet, the sheet materials are plastically deformed, and the material of the sheets gradually fills the cavity of the bottom dies to form the initial clinched joint. The important parameters of the initial clinched joint are mainly the interlock (í µí±¡ í µí± ), the neck thickness (í µí±¡ í µí±› ) and the thickness of the bottom (í µí±‹). The bottom thickness (X) of the initial clinched joint is controlled by the force at first stroke. In the second stroke, the double flap gaskets are removed, leaving the room for the ring to move downward. The flat die is employed to press upper sheet of the initial clinched joint, forcing the bottom ring to move downward. The anvil acts upward on the protuberances of the initial clinched joint, making the materials of the protuberances to flow inward and gradually flatten the protuberances. The TFC joints are formed and automatically demolded. As shown in Fig. 2(b), the protuberance material of the joint flows to the hollow of the joint, so that the cross section of the TFC joint forms a funnel shape. The main parameters of the TFC joint also

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... demonstrated in Fig. 2, the TFC process includes two strokes. The purpose of the first strokes is to form a mechanical clinched joint. The second stroke flattens the protuberance of the mechanical clinched joints. Clinching tools were used in TFC process, including blank holder, punch, double flap gaskets, bottom ring, flat die and anvil. The bottom ring was ...