Issues surrounding lateral stress measurements in alumina ceramics

Plate impact experiments have been performed on alumina ceramics and lateral stresses measured by means of embedded manganin gauges. It is shown that the sample and flyer plate configuration can have a large effect on the form of the lateral stress wave profile obtained. Within a certain stress regime the lateral stress wave profile in alumina ceramics exhibits a two step structure [J. Mech. Phys. Solids 46, 1887 (1998)]. Such profiles have been obtained when impacts are performed using copper flyer plates and stress gauges are mounted close (< ca. 5 mm) to the impact face. We now show that this second rise in lateral stress is not evident when either a ceramic flyer plate is employed or a thin ceramic cover plate is mounted on the front of the target.