Inductive heating of materials for the study of high temperature mechanical properties

Abstract

In high-energy pulsed power applications, the metallic conductors are expected to heat up significantly due to resistive losses. In the pulsed case, materials exposed to short loading times, from 0.1 μs to 100ms behave different from those exposed to long loading times, 1 min to 1 h. With this in mind, it is important to understand the mechanical properties of metals when they are heated rapidly so that the correct mechanical properties are considered when designing high-energy experiments where the thermal and mechanical stresses are high. An expanding ring experiment, similar to the one originally designed by Gourdin et al has been set up at the Institute for Advanced Technology (IAT) to test such mechanical properties. In Gourdin's work the ring specimen under test sits radially around the center of a primary coil that is driven with a current pulse from a near critically damped RLC circuit. The ring expands and fragments due to the induced electromagnetic forces. In order to determine material properties at elevated temperatures, an inductive heating source has been developed to rapidly heat the ring specimen to temperatures as high as the melting temperature in 10's of milliseconds, immediately prior to the application of electromagnetic expansion forces. The data generated will quantify the sensitivity of material properties to the rate and duration of heating in commonly used materials for development and validation of appropriate constitutive equations.