Abstract
A new electromagnetic blank holder method has been developed by using the Lorentz force to supply a flexible and controllable blank holder force (BHF) for electromagnetic sheet metal forming. The Lorentz force is essentially a pulsed repulsive force generated in the blank holder by the interaction between the pulsed magnetic field and the induced eddy current. In this work, the pulsed electromagnetic blank holder (PEBH) system for electromagnetic sheet metal forming is fabricated and tested. The feasibility and effectiveness of the system have been proven by a series of experiments for forming a workpiece of AA1050-O with a diameter of 440 mm. With the PEBH system, the flange wrinkling of the workpiece is demonstrated to be eliminated, and the material flow of the flange and the deformation behavior of the workpiece can be easily controlled by varying the discharge voltage of the blank holder coil. In addition, experimental results corroborate that the critical flange wrinkling BHF equal to 4.8 ton is the optimal BHF to achieve the optimal material flow and improved formability of the workpiece in the process, and the critical circumferential strain for flange wrinkling is − 4.4%.
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