Advances In High Strain Rate Material Testing
Free (open access)
P. Verleysen, J. Van Slycken, F. Van den Abeele & J. Degrieck
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. Keywords: high strain rate, split Hopkinson bar, Kolsky apparatus, deformation measurement, bending test, steel cord, optimization. 1 Introduction Due to the increased importance of issues related to the safety of for instance passengers during a car crash, or to the protection of buildings prone to terrorist attacks, there is an ever-growing need for reliable experiments providing mechanical properties of materials in impact circumstances. As a consequence, the use of split Hopkinson bar (SHB) devices has increased tremendously in recent years. During a split Hopkinson tensile bar (SHTB) experiment, a small material sample is subjected to a uniaxial tensile load at a high rate of strain.
high strain rate, split Hopkinson bar, Kolsky apparatus, deformation measurement, bending test, steel cord, optimization.