A triple-coil electromagnetic two-step forming method for tube fitting

Electromagnetic forming (EMF) is widely used in the processing of tube fittings in the fields of aerospace, automobile, and other industrial manufacturing because of its high energy rate, which can significantly improve the forming limit of light-weight metal materials. One typical application of EMF is the tube attraction by a double-coil electromagnetic single-step (DCSS) forming method. However, the electromagnetic force in this method is unevenly distributed on the tube, which will affect the uniformity of the final shape and undermine the performance of the workpiece. To solve this problem, a triple-coil two-step forming (TCTS) method is proposed in this paper. An electromagnetic-structure coupling finite element model is established to analyze the forming process in both DCSS and TCTS methods; the tube forming uniformity in both methods is compared. To quantify the uniformity of tube, the forming uniform length, D_uniform, is introduced and the area where the deformation is greater than 99% of the maximum deformation is defined as the forming uniform length. The simulation results show that when using the DCSS method, D_uniformD=3.73mm, and when using TCTS method, D_uniformT=11.63mm. The TCTS method increases the forming uniform length by 211%. All these results indicate the potential and the prospect of TCTS method for improving the forming uniformity of tube fittings.