محاسبه عددي ضريب خودالقايي معادل سيم‌پيچ در فرآيند انبساط الكترومغناطيسي استوانه‌

Numerical Calculation of Equivalent Self-inductance Coefficient in Electromagnetic Tube Expansion Process

Self-inductance coefficient is one of the most important parameters in electromagnetic forming process. Presence of workpiece near coil, in electromagnetic forming process, affects the coil self-inductance coefficient seriously and therefore other process parameters such as electrical current amplitude, frequency and pressure applied on the workpiece are affected too. In this paper, the coil-workpiece equivalent self-inductance coefficient, which has not been calculated in previous relevant works, is calculated numerically using a commercial FE code. To obtain the electrical current distribution profile in the coil cross sections, first a cylindrical coil is simulated without any workpiece. Then its self-inductance coefficient is compared with analytical calculation results. By using simulation results, the variation of magnetic-flow versus electrical-current has been plotted. The curve slope (self-inductance coefficient) has been extracted by using least squares method. The calculated self-inductance coefficients of the coils with various dimensions show a good agreement with analytical results presented in other references. Next, this method is used to simulate and calculate the coil-workpiece equivalent self-inductance coefficient in electromagnetic tube expansion process. At the end, as a parametric study, workpieces with various diameters are simulated and their equivalent self-inductance coefficients are calculated. The results agree with the experimental results due to the presence of an external conductive case around a cylindrical coil, which has already been presented in the literature.