MODELING OF ULTRASONIC TRANSDUCER BEAMS U SING A PULSED ANGULAR SPECTRUM

In the scope of ultrasonic non destructive testing, the knowledge of t he field of the transducer in the material to be tested is essential t o locate the detected flaw and moreover to evaluate them in a precise way, We have developed a model based upon a decomposition into plane w aves (angular spectrum), but while this is classically achieved for mo nochromatic fields, we have extended the formalism to transient domain . The first steps of the calculation are classical ; from the knowledg e of the transient field into a plane, a time Fourier transform permit s the decompostion into monochromatic waves, then a spatial Fourier tr ansform gives the decomposition into plane waves. Then it is possible to obtain the transient angular spectrum by mean of a change of variab le and a time recomposition. The recomposition at any point of the fie ld is then no more than a summation, with suitable delays, of all thes e plane waves. The advantage of this method is that the decomposition into transient plane waves (the longest operation) has to be performed only once for a given transducer, since the fit to arbitrary geometri cal configurations (interface, incidence angle,...) is taken into acco unt only at the step of the final recomposition.