Masaki Ishibashi

Electromagnetic Bulging of Stainless Steel Sheet by Using Flat One-Turn Coil

In this paper, we describe an electromagnetic bulging for a SUS304-O stainless steel sheet (0.15 mm thick) and its experimental results. In the die forming, the flat one-turn coil is adopted for the bulging of the SUS304-O sheet, when an aluminum sheet (0.3 mm thick) as a driving plate (driver) is used together. When an impulse current from an energy-storing capacitor bank passes through the flat one-turn coil, a high-density magnetic flux is suddenly generated around the coil. Eddy currents are induced in the driver placed on the coil. The SUS304-O sheet is pressed by an electromagnetic force generated in the driver, leading to bulge into a meandering groove with small concave shape. The bank energy required for the bulging of 12mm wide, 60mm long and 0.43mm high is about 4.5 kJ, and the obtained workpiece does not almost have wrinkles and curves.

Influence of Collision Velocity and Collision Time on Joining Property in Welded Sheets Obtained by Magnetic Pulse Welding

In this paper, a number of factors influencing the joining property of sheets welded by a magnetic pulse welding are described. An electromagnetic force deforms a moving sheet, and the height of the sheet is governed by both the force and the properties of the sheet. Some information obtained from the first collision time is very useful, so two sheets with a gap can be joined with each other after the first collision. The relationship between the collision time and the gap length for an aluminum sheet is examined by 2.0kJ discharge energy experiments, and an approximation curve of this relationship is drawn. The velocity of the moving sheet is found by differentiation of the curve. The relationship between shearing load with the welded sheet and the gap length is also examined. Similar results have also been obtained for a copper sheet, and the relationship between the shearing load and the collision velocity has been shown for two materials. It has been clarified that the shearing load is distributed into three areas depending on the collision velocity. Therefore, the collision velocity is the main factor influencing the joining property of welded sheets. It has also been clarified that another influencing factor is the first collision time.