A Direct Impact Tension Bar setup for testing low-impedance materials at intermediate rates of strain

Abstract

This study introduces a Hopkinson bar variation, well-suited for probing low-impedance materials in the intermediate strain-rate regime. Currently, servo-hydraulic machines (SHM) and drop weight towers are considered primary for measuring mechanical properties at strain-rates 101 to 102/s. However, such setups often exhibit detrimental oscillations due to inertial response. These oscillations can be severe, rendering recorded data unreliable for inferring strain-rate effects. Our Direct Impact Tension Bar (DITB) offers accurate force signals devoid of ringing artefacts. The setup has a long 16 ms pulse duration, facilitating intermediate strain-rate tensile tests on extended ductile specimens. We discuss the DITB construction breakdown and demonstrate its applicability through dynamic tensile tests on sheet-type polycarbonate (PC) specimens at 150/s, compared to servo-hydraulic data. DITB results yield high-quality data, free from oscillations.