Simple modelling of ultrasonic waves from direct- and water-coupled transducers

Earlier work that gave simple expressions for the dominant shear and compression waves produced by an arbitrary transducer has been extended to include a near-field “third term” that eliminates one of the major earlier sources of error. The authors compare the predictions produced by the earlier model and the newly extended model with results obtained from experiments, from computationally intensive exact solutions, and from finite difference calculations. Different sorts of transducer loading are considered, including so-called “Plane Wave Only” and “Edge Wave Only” devices. These enable them to quantify the regions of parameters in which the simpler models are valid. The earlier analysis is extended to include the effects of water-coupling of the transducer. Here too the simpler models produce remarkably accurate results, which should make them extremely useful in practical NDT investigations