An ultrasonic array technique for velocity of bulk waves and sample thickness measurement

The ultrasonic array technique for simultaneous measurement of the bulk wave velocity and thickness of a plate sample is proposed. In the proposed methods, the elements of the array send waves toward the specimen and receive echoes reflected from the front and back surfaces of the sample. The full array data set is used for calculation of the responses of the longitudinal and shear plane waves in the "angle of incidence - time" space. The unknown parameters of the specimen can be estimated by fitting the theoretical model for the time delays of these responses to the experimental data. The 32-element linear array, having a central frequency of 15 MHz, was used in the experiment. It was found that the relative errors of the velocity and thickness measurements are in a range of 1-2%.