5. Self piercing riveting of solid core bolt: the plate to be connected is fixed in the middle of the cavity and the edge band. According to the downward fitness movement of the punching needle, the solid bolt will pass through the upper and lower plates, and break a small piece of metal material. Then, under the back impact force of the upper die, a part of the raw material of the next layer of plate is pressed into the annular pipe groove to produce a self-locking interlocking structure. Self piercing riveting of solid core bolt is a typical process of partial plastic deformation and large deformation, which includes the whole process of punching shear cutting and extrusion forming. Advantages: low cost, high connection quality. Defects: high noise in riveting, geometric shape of bolt, edge banding force of double drum head rivet, gap between bolt and cavity (upper die) have great harm to riveting quality.

6. Self piercing riveting of half space central bolt: when the half space central bolt is pressed down by the punching needle, the bolt passes through the top plate. Under the mutual effect of cavity and punching needle, the end of bolt extends in the next layer of metal material, and a self-locking interlocking structure of mechanical equipment is formed between the two plates. Pay attention to the self piercing riveting process of half space center bolt, when riveting double-layer same metal composite material, the thicker one is put to the next layer; when riveting the double-layer different metal composite material, put the raw material with good plastic deformation into the next layer; when riveting the metal material and non-metal material, put the metal composite material down one layer. Advantages: color rivets can connect double-layer raw materials, without pre drilling, fatigue resistance, less harm to the environment, conducive to quality inspection. Compared with solid core bolt self piercing riveting, it has no flame, no waste, energy saving and low noise. Defects: high precision of mold processing, matching of bolt and plate characteristics.