Optimization of Combined Deep Drawing and Electromagnetic Corner Fill Process of DP980 steel sheet

Abstract

DP980 steel sheet is one of advanced high strength steel sheets (AHSS) introduced in order to achieve both enhanced crashworthiness and lightweight design of auto-body. Due to its comparatively poor formability, the application of DP980 steel sheet to autobody is limited with conventional deep drawing processes. One of remedies is a combined deep drawing and electromagnetic sheet metal forming process, which is one of the innovative forming methods to improve the formability. The process chosen in this paper consists of square cup drawing of DP980 1.2t steel sheet with punch radius of 30 mm firstly and electromagnetic corner fill process to reduce the radius to 10 mm. This paper proposes an approach for numerical optimization of combined deep drawing and electromagnetic corner fill process of DP980 steel sheet. The numerical optimization was conducted by following procedures of optimization of electromagnetic forming force and coil design. Conventional square cup drawing analysis was conducted first and the target function and constraint function were established to minimize the deviation from an ideal shape without violating forming limits for optimization of the EMF force. Then, coil design was carried out for small loss of electrical power transmission. Numerical results and conclusions are demonstrated for the applicability of this combined forming process.