An Apparatus for Tensile Characterization of Materials within the Upper Intermediate Strain Rate Regime

A new “Drop-Hopkinson bar” apparatus has been successfully developed for material tensile property characterization at intermediate strain rates. This new apparatus design combines a drop table, which generates a relatively long and stable low-speed impact to the specimen, with a Hopkinson bar, which provides the load history while accounting for inertia effect in the system. The inertia effect in the specimen was minimized through pulse shaping. The pulse shaping technique was also used to facilitate constant strain rate in the specimen. The newly developed apparatus for intermediate-strain-rate tests was experimentally verified by comparing the tensile stress-strain responses of two materials, 6061-T6 aluminum and 304L stainless steel, obtained from the new apparatus and the conventional Kolsky tension bar, respectively, at the same strain rate of ~600 s−1. The results showed that the new apparatus apparatus is reliable and repeatable for intermediate strain-rate testing as well as comparable to Kolsky bar measurements. The 6061-T6 aluminum and 304L stainless steel were also characterized at low, intermediate, and high strain rates with MTS, the new apparatus, and Kolsky tension bar, respectively, to determine the effect of strain rate on tensile stress-strain response for both materials.