Ultrasonic Measurement of the Dynamic Elastic Moduli of Small Metal Samples

Ultrasonic velocity measurements were used to determine the dynamic elastic moduli of small metal samples to a 2σ measurement uncertainty of better than 1%. The samples were cylindrical in shape, possessing nominal diameters of 12 mm and thicknesses of 6 mm. Aluminum, titanium, and stainless steel compositions were examined. In the longitudinal wave measurements, a 20-MHz quartz piezoelectric element transducer was employed in pulse-echo mode using a tone-burst excitation. These longitudinal time-of-flight measurements were made with a repeatable 2σ measurement uncertainty of [less-than or equal to] 1.0 ns. Shear time-of-flight measurements, using a 10-MHz contact ceramic piezoelectric element transducer subjected to tone-burst excitation, were made with a repeatable 2σ measurement uncertainty of approximately equals 2.0 ns. NIST calibration facilities provided measurements for the density and lengths of these samples, as needed for the moduli calculations. Results indicate that the measurement uncertainties for elastic moduli measurements of this type can be kept quite small.