电流丝法在电磁成形线圈电流和工件电磁力计算中的应用

Application of Current Filament Method on the Calculation of Current and Force in Electromagnetic Forming

电磁成形系统中线圈放电电流和工件电磁力的精确求解对于探究工件的动态变形行为及优化电磁参数至关重要。目前有限元法被广泛用于计算上述两个参数,但在电磁场-结构场耦合计算的过程中,当工件存在大/复杂变形时易引起空气网格畸变,进而导致电磁计算精度低、收敛性差及计算耗时长等问题。为此,基于电流丝法研究电磁成形线圈电流和工件电磁力的求解方法,并以COMSOL有限元数值分析结果为基准对比分析传统型和改进型电流丝法的求解性能。研究表明,所提出的改进型电流丝法因对线圈各匝导线进行了细分而显著提升了等效电路模型中丝单元互感及互感梯度的计算精度,进而能更准确地反映趋肤效应下的线圈电流和工件电磁力分布特征。在此基础上,探究改进型电流丝法在不同放电频率、导线尺寸及工件形状等条件下的参数求解性能,进一步验证了所提方法在电磁成形系统中的有效性和适用性。

Accurate calculations of coil current and electromagnetic force in the workpiece in electromagnetic forming(EMF)system are essential to analyze the dynamic behavior of workpiece and optimize electromagnetic parameters.By now,finite element method(FEM)has been widely applied to simulate these two parameters.However,when the coupling analysis of electromagnetic and structure fields is carried out using FEM,large or complicated workpiece deformation can easily cause the air mesh distortion,which leads to low accuracy,poor convergence and long simulation time.Therefore,this paper studies the calculation of coil current and electromagnetic force in workpiece in EMF based on current filament method(CFM).Taken the numerical results by COMSOL as references,comparative analysis of the conventional and improved CFMs is carried out.The results show that the improved CFM proposed in this work can reflect the distribution characteristics of coil current and electromagnetic force in workpiece more accurately with considering the skin effect.It is because the computational accuracy of mutual inductances as well as their gradients of each current filament in the equivalent circuit has been improved when each coil turn was divided into several parts.On this basis,the validity and applicability of the proposed method for EMF are verified by analyzing the computational performance under different discharge frequencies,coil conductor sizes and workpiece geometries.