The Theoretical Research on the Blanking of the Sheet Material : Part 1, Analysis of the Statically Admissible Stress Field

Abstract

The author applied the theory of limit analysis to a theoretical investigation of the stress distribution in the sheet material during circular blanking, and calculated the statically admissible stress distribution on the following assumptions : (1) The sheet material is the non-hardening plastic-rigid body. (2) The ratio of the tool diameter to the sheet thickness is large enough to be assumed that the material near tool edges is approximately in the state of plane strain. (3) Stresses in the material caused by punch are equal to that by die. (4) The stress field in the material consists of several regions of constant stress separated by straight lines of discontinuity. As the result of the analysis, many actual blanking characters were well explained, and the lower bound of the blanking force, the side force acting on the die, etc., could be reasonably estimated.