Title :
Time recompression of dispersive Lamb waves using a time reversal mirror-application to flaw detection in thin plates
Author :
Ing, Ros K. ; Fink, Mathias
Author_Institution :
Lab. Ondes et Acoustique, Paris VII Univ., France
Abstract :
In this paper, the time reversal processing is applied to compensate for the effect of dispersive Lamb waves. A time reversal mirror, made of a 32 element transducer array is coupled to a Duralumin plate with a Plexiglas wedge. In the first experiment, a Nd-YAG laser is used to create a point source of Lamb waves. The transmitted pulse is then recorded and time-reversed by the array and both time recompression and spatial refocusing are observed at the source point. In the second part of this paper, flaw detection in plate is performed with a pulse echo time reversal technique and we show the effectiveness of this technique to enhance the signal to noise ratio
Keywords :
dispersion (wave); flaw detection; surface acoustic wave signal processing; surface acoustic wave transducers; ultrasonic dispersion; ultrasonic focusing; ultrasonic materials testing; ultrasonic transducer arrays; 32 element transducer array; 4 MHz; Duralumin plate; Lamb wave point source; Nd-YAG laser; Plexiglas wedge; dispersive Lamb waves; flaw detection; pulse echo time reversal technique; signal to noise ratio enhancement; spatial refocusing; thin plates; time recompression; time reversal mirror; transmitted pulse; Bandwidth; Dispersion; Frequency; Inspection; Mirrors; Optical arrays; Optical coupling; Surface emitting lasers; Time measurement; Transducers;
Conference_Titel :
Ultrasonics Symposium, 1996. Proceedings., 1996 IEEE
Conference_Location :
San Antonio, TX
Print_ISBN :
0-7803-3615-1
DOI :
10.1109/ULTSYM.1996.584061
