Research on Formability of Multi-Point Press Forming for 08Al and 2024-O Sheet

Abstract

Unlike multi-point die forming (MPDF), multi-point press forming (MPPF) takes full advantage of the flexibility of multi-point forming (MPF). In the process of MPPF, the punch elements always keep in contact with the sheet metal, developing instantaneous forming surfaces, which clamp and deform the plates. In this study, based on the spherical surfaces, the formability of both MPPF and MPDF were simulated through finite element software. The effects of the two methods on dimple, wrinkle and springback defect were comparatively analyzed. Also the shape error of MPPF was studied. We find MPPF can significantly inhibit dimple and wrinkle, thus obviously reducing the maximum strain and homogenizing the distributions of stress and strain of the parts. The largest vertical springback value decreases from 0.514mm to 0.257mm and the stress is released more completely after unloading. The edge effect reduces the curvature in the area far away from the center, greatly magnifying the shape error. The increase in the numbers of punch elements and in the dimensions of elastic cushions can significantly weaken the edge effect and improve the forming precision. These analyses show MPPF has better formability for metal sheets than MPDF.