Lamb wave mode decomposition using concentric ring and circular piezoelectric transducers

Lamb wave mode decomposition using annular transducers and quadrature signals

“…The mode coefficients for a given transducer pair should not be a function of the separation distance between them, as was previously shown in [8]. Here, to investigate any dependence of mode separation on transducer separation distance, signals recorded at distances of 381 and 559 mm were decomposed in two different ways.…”

“…It is assumed that the underlying symmetric and antisymmetric mode signals, s(t) and a(t), respectively, can be represented as linear combinations of the tone burst responses and their quadrature signals, 8 8…”

“…Also, separation coefficients were optimized for echoes with specific dispersed shapes. Since these shapes are a function of element size (and thus element pair) [8], lack of compensation for this may result in distance dependent effects since signal shapes change with distance. …”

“…One strategy [8], which served as the foundation for this work, accomplished mode separation by using two-element annular transducers (i.e., an inner disk surrounded by an outer ring). The measured signals that resulted from different combinations of the two transducer elements were modeled as a linear combination of underlying symmetric (S 0 ) and antisymmetric (A 0 ) Lamb wave modes.…”

Delamination detection in a composite plate using a dual piezoelectric transducer network

“…The development of the proposed technique is based on the premise that the fundamental anti-symmetric mode (A 0 ) slows down when it passes through a delamination area while the speed of the fundamental symmetric mode (S 0 ) is invariant of delamination. In order to extract a delamination sensitive Lamb wave mode from measured Lamb wave signals, a mode extraction technique using dual PZTs, which are composed of ring and circular PZTs, is proposed based on the mode decomposition technique developed by authors [14]. For the damage diagnosis, instantaneous outlier analysis is proposed so that a damage threshold can be automatically computed only using current data.…”