Material Flow Analysis of Tearing Failure in Fine-blanking Process

Abstract

A fine-blanking technology is well known as an effective and economical blanking process becausethis process could obtain a clean cut surface with a high accuracy. Therefore, the secondary processsuch as a machining process is eliminated. From these advantages on the fine-blanking, nowadays, it isgenerally used in many industrial fields such as the automobile industry and the electronic industry. Theseadvantages, over a conventional blanking, are possible due to a high blank holder force, a high counterpunchforce, a small clearance and a large die cutting edge radius. However, the selection on those parametervalues affects on the material flow and the cut surface on the blanked parts also. Namely, it causes thecrack formations and tearing failure which are the general problems in the fine-blanking process.

In this study, therefore, the material flow analysis was investigated in order to study the formationof the tearing failure and the cut surface with respect to the several blank holder and counterpunch forcesby using the finite element method (FEM). From the results, it indicated that the increasing of the blankholder and counterpunch forces result in the rotating movement in the material. This movement increasedthe hydrostatic pressure in material and also made the material gone difficultly into the shearing zone;therefore, the crack formation was stopped and the secondary shear surface occurred. Namely, thetearing failure was formed. Furthermore, the FEM simulation results were verified by the experimentsand they were well agree with each other. It indicated that the FEM simulation could be a useful tool forpredicting the cut surface features in the fine-blanking process.