Ultrasonic Measurement of the Dynamic Elastic Moduli of Small Metal Samples
John A. Slotwinski, Gerald V. Blessing
Ultrasonic velocity measurements were used to determine the dynamic elastic moduli small metal samples to a 2[sigma] measurement uncertainty of less than one percent. 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 2[sigma] measurement uncertainty of [GE] 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 2[sigma] measurement uncertainty of = 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.