Method for Punching Holes in Brittle Sheet Materials. Modeling of Punching Operation and Basic Experiments.

The purpose of the present research is to establish a simple method of forming holes in brittle sheet materials by a conventional punching technique. By utilizing a specially designed round-top punch, a small hole is formed at the center of the sheet specimen at its first stage, and subsequently the hole is enlarged by a continuous punching operation. The present improved technique realizes a very low load for punching operation as well as a considerably low precompression stress for preventing serious radial cracks around the hole. The technique is also successful in forming many holes by a single operation.