A mode-conversion method for evaluating elastic properties of materials

An ultrasonic apparatus for evaluating elastic moduli of materials was designed. The problem of measuring shear-wave velocity, which could be difficult to overcome with equipment using shear-wave transducers, was solved by a transducer-cell. In this latter, only a compressional wave transducer was used. The specimen is in the form of a prism, and the angle arrangement of the specimen and the transducer allowed compressional waves to be refracted either as compressional or shear waves, depending on the angle of incidence of the sound beam on the liquid-solid interface. Thus, both velocities could be computed in a relatively simple manner with the help of a special formula, which contains only easily measured variables. The device can be used with existing flaw detectors which are based on transit-time measurement of a pulse-echo. It could also be linked to a computer through a computer interface in order to make a semi-automated system for computing and displaying elastic constants of materials. The author used no off-the-shelf equipment: in addition to the transducer-cell, which is the subject of this paper; he designed a transducer holder; a power amplifier, a frequency synthesiser; a computer interface, and wrote a computer program in order to control the whole experiment.