かえりなしせん断加工の成功条件および切り口面品質に及ぼす材料延性の影響

Abstract

In push-back blanking, burr-free products are produced by compressing a half-blanked sheet between platens, where success conditions are affected by the ductility of materials. In this study, the mechanism of success and the cut edge quality in the push-back blanking process using a ductile and a brittle steel sheet were discussed. Experiments were carried out, varying the punch penetration and clearance in the half-blanking step. Brittle steel showed a wider successful range and less shear droop on the cut edge than ductile steel. Corresponding simulations were conducted and the damage value based on a ductile fracture criterion was calculated around the shear zone. Negative clearance was effective in keeping the damage value low and allowed deep punch penetration without fracturing in the half-blanking step. In the following push-back step, a rapid increase in the damage was observed when the high mean stress zone prevailed over the half-blanked portion. The timing of increase in damage was earlier for brittle steel owing to the localization of deformation, resulting in a wider successful range than that of ductile steel.