Dynamic Properties of Geologic Specimens Subjected to Split-Hopkinson Pressure Bar Compression Testing at the University of Kentucky

Abstract

Advances in materials science have shown that material behavior varies according to the rate of load application (strain-rate sensitivity). With regards to compressive strength, materials have been observed to exhibit a strengthening, weakening, or negligible response to increasing strain-rates (Zhang and Zhao in Rock Mech Rock Eng 47(4):1411–1478, 2014). Practical experimentation to ascertain these responses has been carried out for over a century, based on the fundamental equipment design pioneered by John Hopkinson in 1872 and modified by Kolsky in 1949. A contemporary Split-Hopkinson Pressure Bar (SHPB) has been constructed at the University of Kentucky (UKY) to research the dynamic properties of various geologic materials for mining and civil engineering applications. Geologic samples are of an inconsistent nature due to inherent discontinuities and large grain size. To ensure test specimens are of adequate size to reflect this inconsistent nature, the SHPB at the UKY has been constructed with component bars of 2 in. (5.08 cm) diameter. Prior publications have discussed various considerations associated with the testing procedure and data processing of this SHPB (dispersion correction, pulse shaping, etc.) (Silva and Lamont 2017). This publication presents the results of materials testing with this SHPB. Three materials were selected: Bedford (Indiana) Limestone, Berea (Ohio) Sandstone, and Aluminum 6061-T6. Two of these are common aggregates found in the mining and construction industries, while the third is an aluminum variant often encountered in industrial applications. Dynamic compression testing of these materials at various strain rates was carried out, and the results are included. Static test results have been included for comparison, and the testing and data analysis procedure are discussed in detail.