Influence of modal characteristics of a partially debonded piezoelectric transducer in higher and subharmonic modes generated in Lamb wave

Noncumulative higher and subharmonic Lamb wave modes generated as a result of partial de-bonding of piezoelectric wafer transducers (PWT) is numerically investigated and experimentally validated. The influence of excitation frequency on the extent of nonlinear interaction as a result of partially de-bonded PWTs is discussed. A set of specific frequency ranges is arrived at based on the eigenvalue and harmonic analyses of PWTs used in this study. These are the frequency ranges in which resonant width direction modes of a square PWT or radial modes of a circular PWT are seen. In these frequency ranges, significantly high amplitudes of higher and subharmonics are observed. It is also seen that in these frequency ranges, subharmonic and higher harmonic amplitudes are dependent on de-bond length and location. Signal processing is carried out using normalized fast Fourier transform for relative comparisons.