2020 Volume 61 Issue 718 Pages 219-225
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.
