Dynamic Ductility and Fragmentation for Aluminum Alloy Using Electromagnetic Ring Expansion

Abstract

In order to investigate the effects of ductility enhancement for aluminum alloy under the high-velocity EMF condition, the electromagnetic ring expansion test is carried out. Through a use of Photron digital high-speed video camera, the sequence of deformation and failure in the expanding ring are determined. Subsequently, the variation of expansion velocity with time is measured. In particular, this work reveals the effects of expansion velocity on the ductility, necking characteristic, fracture behavior of Al 5052-O and 6061-T4. In addition, the dynamic ductility of Al 5052-O under electromagnetic ring expansion experiment is compared with that in split Hopkinson tension bar (SHTB) test and quasi-static tensile case. It is shown that the number of necks and fragments increase as the maximum expansion velocity increases. Furthermore, the uniform strain and fracture strain augment with increasing expansion velocity, which is more evident for Al 5052-O. The fracture surfaces of ring fragments are characterized by the larger and deeper dimple-like structure at higher expansion velocity. Compared with the SHTB tests at the same strain rate, the ductility of Al 5052-O under electromagnetic ring expansion is better. The ductility enhancement results from not only the inertia effect but also the changes in material constitutive behavior.