Two-way crack propagation and separation mechanism of packaging steel strip

Two-way crack propagation and separation mechanism of packaging steel strip
The punching process of the 'two-way crack propagation and separation' mechanism can be divided into the following three stages:
　　 The first stage is the elastic deformation stage. At the beginning of blanking, after the punch contacts the material, due to the pressure of the punch, the material is elastically compressed and bent, and slightly squeezed into the cavity of the concave mold. At this time, the internal stress of the material does not exceed the elastic limit.
　　 The second stage is the plastic deformation stage. When the punch continues to pressurize and the internal stress of the material reaches the yield limit, part of the metal is squeezed into the cavity of the concave mold, causing plastic deformation. Because there is a gap between the convex and concave molds, the material is bent and stretched at the same time, so when the convex mold continues to pressurize, the internal stress of the material will increase continuously, and the material at the edge of the convex and concave molds will be concentrated. When the internal stress exceeds the shear strength of the material, the material at the stress concentration will crack.
　　 The third stage is the tearing stage. When the punch continues to pressurize, the material cracks at the edge of the convex and concave molds will continue to expand into the material, and the material will be pulled apart immediately. When the gap value is reasonable, the upper and lower cracks coincide with each other.
　　Because the thin plate punching die still belongs to the gap blanking, its convex and concave die materials are quenched steel, and the cutting edge part is relatively sharp, so the 'two-way crack propagation and separation' mechanism is suitable for thin plate punching dies.