Guided waves analysis using multiemitter and multireceiver arrays.

Abstract

Structural and material properties of elastic waveguides can be characterized by fitting measured to theoretical guided wave phase velocities. Here emitters and receivers are placed in contact on the same side of the waveguide (i.e., axial transmission geometry). Multireceiver arrays allow the determination of phase velocities using two‐dimensional spatial‐temporal Fourier transform, which requires a large distance probed by the receivers. Practical constraints, as in clinical inspection of cortical bones, may reduce the inspected spatial length and therefore the efficiency of this technique. We propose a technique which takes benefit of using both multiple emitters and multiple receivers. This approach derived from the DORT method adapted to the transmission problem. The singular values decomposition at different frequencies of the transmission matrix between the arrays give the invariants of transmission, which are linked with the guided modes. First, experiments carried out on different metallic plates are shown. Experimental velocities are in good agreement with Lamb waves theoretical values. In particular, zero group velocity resonance and negative phase velocities are shown. These results allows a good evaluation of the thickness and the transverse and longitudinal bulk waves velocities. Further applications concerning evaluation of elastic properties of cortical bone are finally mentioned.