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Talking about the influence of the necking process in the processing of metal stamping parts

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In the process of shrinking, the metal stamping material at the shrinking end slides into the die under the pressure of the punch to reduce the diameter and increase the wall thickness and height. It can be approximated that the deformation region is in a state of plane stress under positive pressure in both tangential and radial directions, and the tangential pressure is the main force. The radial compressive strain is the maximum strain, while the thickness and length directions are elongation deformation, and the deformation amount in the thickness direction is more than that in the length direction.

Due to the action of tangential compressive stress, the billet is easily unstable and wrinkled during the shrinking process; at the same time, the wall of the non-deformed area is also prone to instability and deformation due to all the shrinking pressure. Therefore, preventing instability is shrinking. The main problem with the process.

The ultimate deformation degree of the necking is mainly limited by the buckling conditions. The degree of deformation of the necking depends on the necking coefficient of the material. It is expressed by the total shrinkage coefficient ms:

ms = d/D     where

ms—total shrinkage coefficient, d—diameter after shrinkage; D—diameter before shrinkage.

The size of the shrinkage coefficient is related to the mechanical properties of the material, the thickness of the material, the form of the mold, the surface quality, the edge of the shrinkage end of the part and the lubrication conditions. The comprehensive mouth coefficient of various materials can be obtained through the relevant information table.

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