Time-Delay Periodic Linear Array: A unidirectional guided wave transducer for ultrasonic NDT applications

Zhu, Wenhao; Chahbaz, A.; Brassard, M.
May 2000
AIP Conference Proceedings;2000, Vol. 509 Issue 1, p1057
Academic Journal
Due to their improved mode selectivity and small geometrical size, linear-array transducers have recently found increasing application in guided wave NDT of metallic structures. In this paper, simple and flexible Time-Delay Periodic Linear Array (TDPLA) designs are described and used for guided wave inspection of different metallic structures. Using wave interference effect, unidirectional guided wave excitation and reception are achieved. Several TDPLA patterns are experimentally tested to produce different guided modes. The unidirectional TDPLA transducer has been applied to detect defects (cracks and notches) in metallic structures in a pulse-echo scheme. Experimental results from several specimens are also compared to those obtained from tests using conventional wedge transducers. Compared to bi-directional linear arrays (such as combs and interdigital arrays), which emit guided waves at both sides of arrays, time-delay periodic arrays generate efficiently guided modes with high wave energy concentration at one side and avoid the unnecessary wave emission at the other side. © 2000 American Institute of Physics.


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