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

Abstract

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 moduli and Poisson's ratio to be computed to a comparable accuracy. Comparison of results with published data for 4340 steel, fused-quartz, and aluminum 6061-T6 is excellent 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 pathlength), brass, lucite, steel, fused silica, glass, and thoriated tungsten. Mode conversion by reflection or refraction has also been used to measure shear-wave velocity, but this is not required. The momentary contact method is amenable to production-line inspection and quality-control situations where measurements of material integrity, temperature, or flaws are required at room or elevated temperatures. [This work was supported by the U. S. Office of Naval Research.]