To measure the forming limit strains of metal tubes under biaxial deformation, a new bulging test, the partial onesided rubber bulging test, was proposed. In this test, a tube is locally bulged at the opening using a rubber pressure medium. Since a sealing mechanism is unnecessary, different from hydraulic pressure bulging, the proposed test can be carried out easily using only a universal compression test machine and a simple container. In the circumferential and axial strain space, some strain paths between equi-biaxial tension and uniaxial tension can be measured. In this research, we experimentally examined two methods of obtaining various strain paths. One is to form a rectangular cutout on the tube specimen at the side opposite to the opening. We found that this method enables us to obtain some strain paths between plane strain tension and equi-biaxial tension. The other method is to form a slit in the vicinity of the opening in the axial direction. The strain path obtained with the slit was that between uniaxial tension and plane strain deformation. We applied the proposed method to an A1070TD pure aluminum tube and confirmed by image processing analysis that multiple strain paths in the local bulged region could be obtained by the proposed method.
In this paper, we describe the relationship between the cross-sectional shapes of two coils and the joining property of sheets welded by magnetic pulse welding. The two coils are each made of one copper alloy plate, and their cross sections are a rectangle and a trapezoid. The coil with a rectangular section is usually used because electromagnetic coupling between the coil and a moving sheet is close. The welded sheet is joined by two welded lines with a void between the two lines. If the thickness of the moving sheet is small, the void becomes wide and the joining width on the two welded lines becomes smaller. This problem is improved by using a coil with a trapezoidal edge section. This shape of the coil changes the distribution of the electromagnetic force generated in the moving sheet. As a result, joining starts sooner on the two sheets and the void width in the welded sheet obtained decreases. In the case of a thin moving sheet, the coil with the trapezoidal edge section increases the joining width in the resulting welded sheet and lessens the joining resistance.