Microstructural Effects in the High Strain Rate Ring Fragmentation of Copper

Abstract

Understanding the failure of rings and shells at high strain rates is a longstanding challenge (Mott, N.F. (1947), Fragmentation of rings and shells, Proc. Royal Soc., A189, 300--308, January.). Predicting the distribution of fragment sizes, shapes and velocities has been an important objective for the many modelling techniques applied to the problem; a detailed history of this research can be found in the work of Grady (Grady, Fragmentation of rings and shells. Springer, Berlin Heidelberg, 2006). Physical testing is particularly important for model development and validation. More recently, ring fragmentation has been used to study the relationship between material microstructure and dynamic fracture.

A series of explosively loaded fragmentation experiments were conducted to investigate microstructural effects in the dynamic tensile behaviour of high purity copper. Rings of high purity copper were expanded at strain rates of approximately 10⁴ s⁻¹. Diagnostics include PDV, high speed photography and soft capture. The fracture mechanism is studied through the detailed analysis of fracture surfaces and fragments using scanning electron microscopy. Microstructural changes induced by the plastic deformation developed during the applied loading are also examined.