A Joule Heated High-Temperature Tensile Split Hopkinson Pressure Bar

Background Extreme application conditions frequently consist of environments involving one or more of the following factors: very high (or low) temperatures, irradiation, corrosive medium exposure, elevated stresses, and high-strain-rate loading. Due to challenges in replicating environments where more than one factor is present, experiments typically are restricted to investigating a single environmental condition. Objective The objective of the efforts outlined herein is to demonstrate the precisely-controlled high-rate heating of a variety of metallic material systems up to one-half their melting temperature within a Tension Split-Hopkinson Pressure Bar (TSHPB). Methods Specific materials investigated include Ti-6Al-4V, Inconel 718, and Magnesium alloy AZ31B. The adopted method integrates a duty-cycle controlled Joule heating system with a TSHPB system. Results Accurate and repeatable heating profiles (i.e., within +/- 5 degrees C of the desired temperature up to 725 degrees C) allow testing without direct temperature monitoring. Combined, the Joule heating system and TSHPB provide an experimental setup capable of strain-rates up to 10(3) s(-1), a heating system that can produce currents up to 250A, resulting in material-specific heating rates exceeding 100 K/s. Constraining heating times to a few seconds limits microstructural changes, thereby suppressing annealing or grain growth processes, resulting in unique, non-equilibrium superheated microstructure states. Conclusion The presented system enables the study of elevated temperature high-strain-rate material behavior, which is relevant to improving understanding of material behavior during high-speed machining, forging, high-velocity vehicle crashes, protection system response to impacts and blast, as well as nuclear energy applications.

Automated summary

This article introduces an experimental setup that allows for precisely-controlled high-rate heating of metallic material systems to study their behavior under high-temperature high-strain-rate conditions. This is important for improving understanding of material behavior during high-speed machining, forging, high-velocity vehicle crashes, protection system response to impacts and blast, as well as nuclear energy applications.