Critical blank-holder force in axisymmetric deep drawing
(1. Key Laboratory of Advanced Forging and Stamping Technology and Science (Ministry of Education),
Yanshan University, Qinhuangdao 066004, China;
2. State Key Laboratory for Fabrication and Process of Nonferrous Metals,
Beijing General Research Institute for Nonferrous Metals, Beijing 100088, China)
Yanshan University, Qinhuangdao 066004, China;
2. State Key Laboratory for Fabrication and Process of Nonferrous Metals,
Beijing General Research Institute for Nonferrous Metals, Beijing 100088, China)
Abstract: An analytical approach for predicting the critical blank holding force (BHF) was presented. Using energy method, the analysis provides the circumferential stress and the equivalent strain as functions of radius under the plane strain and the equivalent strain is inversely proportional to the radius respectively. The maximum relative errors of the circumferential stress and the equivalent strain are 22.3% and 35.9% respectively under the two conditions for some dimensions of sheet and die. In addition, the relationship between BHF and wrinkle number was obtained under the assumption that wrinkle shape is expressed by power function. The critical BHF under plane strain was analyzed for the wrinkle shapes when the power is less than, equal to or greater than 1. The effects of wrinkle shapes on the critical BHF are also presented.
Key words: sheet metal forming; deep drawing; wrinkling; critical blank-holder force; wrinkle model; wrinkle number