Stresses in the punch in the impact pressing of metal powders

Conclusions

The most heavily stressed element of the pressing tool, operating under the most severe conditions, is the upper punch. A dominant influence on the operating life of the punch is exerted by the stress set up in it during impact. In the most heavily stressed, upper part of the punch the compressive stress is a minimum when the striker and punch diameters are equal. The stress diminishes with increasing punch length. Use of a striker with a spherical end face produces a substantial stress concentration in the contact zone, which may lead to the fracture of the punch. Decreasing the radius of the sphere significantly reduces this stress. With increasing impact velocity, the stress in the punch grows. In each specific case the maximum permissible impact velocity is limited by the maximum stress that the punch can withstand.