Ultrasonic Measurement of Elastic Moduli at Elevated Temperatures, using Momentary Contact

The elastic moduli of several materials have been determined by momentarily coupling 1-Mc/sec longitudinal- and shear-wave pulses through a sample and measuring the transit time. The temperature range has been from room temperature to beyond 1000°C. Measurement of longitudinal- and shear-wave velocity is accurate to about 1%, permitting the dynamic moduli to be computed to an accuracy of about 2%. Comparison of results with published data for 4340 steel, fused silica, and 6061-T6 aluminum is good up to the highest temperatures at which data are available. The test sample is a cylinder five wavelengths in diameter by several inches long. Dimensional requirements are easily met. Accordingly, sample preparation and moduli determinations are relatively simple. Momentary coupling of longitudinal waves is achieved by employing a suitable couplant. Shear waves are coupled dry by using special probes. At room temperature, these probes have been used to measure shear-wave velocity in copper, aluminum (up to 60-ft path length), brass, lucite, steel, fused silica, glass, graphite, thoriated tungsten, and other refractory materials. The momentary-contact method is amenable to certain production-line inspection and quality-control situations where measurements of material integrity, temperature, or flaws are required at room or elevated temperatures.