A systematic study was performed on two types of welding circuit with different inductances and one welding coil at five discharge energies for each circuit. The inductance of each circuit was determined by adding its respective remaining inductance and one effective inductance. This study demonstrated a condition necessary for fabricating an A6061-T6/DP590 welded sheet, resulting in a high deformation velocity of an A6061-T6 moving sheet and a large impulse generated on the sheet after the first collision. The three elements of a discharge current are the maximum value, oscillating period and damping coefficient. Compared with the maximum value, the time to the maximum value and the period in the measured discharge currents, the corresponding error rates of discharge currents reproduced by calculation are very low. Therefore, both the magnetic pressure and the impulse calculated from the reproduced discharge currents are highly reliable. The condition affecting the joining strength of the welded sheet was verified from the collision velocity and the impulse. It was clarified that the high collision velocity above 300 m∙s ^-1 and the large impulse from the first collision to approximately 14 μs resulted in the fabrication of the welded sheet with high welding strength.

In magnetic pulse welding, the deformation occurring when a moving sheet collides with a fixed sheet is analyzed following a free deformation analysis of the moving sheet, and a magnetic pressure is used as an input of the moving sheet. In the free deformation analysis, the initial magnetic pressure is calculated for the moving sheet standing still, and the pressure applied to the sheet deforming is renewed by the method of successive approximation. Consequently, the time and velocity calculated at the first collision can be close to the measured values of the standard, and the calculated values are used as the initial values in the deformation analysis with collision. An equivalent stress in the fixed sheet is distributed in a semi-ellipse shape at the early stage after the first collision because the moving sheet deforms in a convex shape. After that, the moving sheet and the fixed sheet vibrate to repeat contacts and separations. As a result, the center of a weld sheet fabricated finally becomes the non-joining. The moving velocity and collision angle at a collision point, which are the joining condition, become constant with time because of the vibration of the two sheets.