Advances in high strain rate material testing

Abstract

In this contribution, attention is focused on new developments and possibilities for advanced material testing using split Hopkinson bar setups. The possibility to test non-common materials (such as small diameter steel cords), and to generate more dimensional stress states (e.g. in a three-point-bending configuration) is outlined. In both tests very low amplitude signals have to be captured. Because measurement devices have become much more sensitive in recent years, these signals can now be measured with sufficient accuracy. Moreover, the technical specifications of high-speed imaging devices have improved tremendously. A technique to extract the deformation of a Hopkinson specimen from high-speed streak camera images - using geometrical Moiré and phase shifting - will be presented. Other advances, made possible by the increased availability of numerical tools, are enhanced signal processing and/or data extraction techniques. Finally, a combined numerical/experimental method to exclude the influence of the specimen geometry on the stress-strain curves extracted from classical Hopkinson experiments is presented.