THE PROPAGATION OF SHORT PULSES OF ULTRASOUND FROM A CIRCULAR SOURCE COUPLED TO AN ISOTROPIC SOLID

New finite-difference formulations in cylindrical coordinates are given allowing calculations to be made of the field radiated by a circular source coupled to an isotropic solid. Theoretically predicted results are compared with earlier theoretical and experimental results for the case of a pointlike source. Calculations of the spacial distribution of the field radiated by a finite-sized circular source are compared with stroboscopic visualizations of the field radiated by a transducer typical of those used in nondestructive evaluation using ultrasound. Calculated field-point particle-velocity waveforms are compared with experimentally measured waveforms received using a miniature piezoelectric receiver directly coupled to the solid surface as well as with calculated results obtained using an impulse-response model. Good agreement between theoretical and experimental results is observed. The field radiated into solids is described in terms of plane and edge waves. The results are of particular significance for explaining the limitations of nondestructive evaluation using ultrasonic pulse-echo techniques. © 1990, Acoustical Society of America. All rights reserved.