Ultrasonic Measurement of Phase and Group Velocity Using Continuous Wave Transmission Techniques

摘要

Phase and group velocities V and U, respectively, were measured in the 100:1 frequency range 50 kHz to 5 MHz using longitudinal and shear ultrasonic continuous waves in teflon and in a dispersive three-dimensional reinforced composite. A new transmission approach was developed which used broadband transducers and a pair of wedges to obtain V by a differential path, fixed frequency technique, and to obtain U by fixed-path, differential frequency technique. The path or frequency was incremented to fit additional whole wavelengths in the path, as indicated by 2pi phase shifts in a Lissajous pattern. Cross-checks between U and V confirmed the validity of the approach at least for the two materials investigated. (Author)