Discretized blank holding driven by electromagnetics for forming complex parts: mechanism, optimization, and validation

Electromagnetic blank holding offers high energy efficiency, flexibility, and high precision in control. By discretizing the electromagnetic blank holder force, the system achieves improved energy efficiency and control performance. However, the influence of this discretization on forming quality remains unclear. To address this issue, a model is established to calculate the discretized blank holder force (DBHF) across different areas based on strain energy conversion, and the mechanism of DBHF discretization is analyzed. The DBHF design for the complex part was proposed through collaboration between an optimization algorithm and finite element analysis to improve forming quality. With the optimal discretization level and the corresponding magnitude, the DBHF can be applied to form the approached multi-channel electromagnetic loading. To validate effectiveness, a car door prototype with various complex features was selected for forming by simulation and experiments. Results showed that the design is efficient for finding the optimal DBHF, reducing the maximum thinning ratio by 3.9%, the maximum thickening ratio by 13.6%, and the maximum strain on the FLC by 43.9% compared with a constant blank holder force. The forming qualities of the part at different discretization levels show an initial increase followed by a decrease. This work contributes to identifying the optimal DBHF for electromagnetic blank holding, thereby improving the quality of manufactured parts.