Determining the Dynamic Elastic Modulus at Elevated Temperatures by Using Rapid Heating Techniques

Abstract

A unique method of determining the dynamic elastic modulus at elevated temperatures is reported. It consists of discharging a low-inductance capacitor bank through a preheated thin rod of the test material, which is clamped at one end and free at the other. The transient i2R heating during bank discharge takes place in a time interval short compared to the mechanical response time of the rod, inducing longitudinal oscillations. The periodic motion of the free end of the rod interrupts a collimated light beam directed over the rod and onto an SD-100 photodiode whose output is recorded on a 561A Tektronix oscilloscope. This gives a direct measure of the modulus since it is inversely proportional to the square of the period of oscillation. The theory, experimental apparatus, and method are discussed and sample data are given for tests made on type 304 stainless steel to illustrate the accuracy and usefulness of this technique. The data are compared with those of other investigators using other methods, and excellent agreement was obtained. This method is particularly useful for testing hazardous materials where remote operation is required for safety.