The transmission of Lamb waves across adhesively bonded lap joints

The transmission of Lamb waves across adhesively bonded lap joints is inves tigated using finite element analysis. The studies consider three modes for excitation and reception, so, ao, and al, applied to lap joints consisting of parallel aluminum sheets bonded with an epoxy adhesive. Transmission co efficient results for a two-dimensional range of bond thicknesses and bond overlap lengths are presented for all three modes. The transmission coeffic ient's are calculated from the spectra of the received and transmitted sign als using an approach which is insensitive to the presence of multimode sig nals and reverberated signals, and which approximates to a power transmissi on coefficient. Detailed analysis is then performed for one of the modes in order to investigate the nature of the mode conversion in the overlap regi on of the joint. It is found that the relative amplitudes of the different modes which propagate in the overlap region can be estimated reliably and s imply from the properties of the incident wave mode. As well as demonstrati ng the physics of the mode conversion behavior, the study provides a basis for the selection of modes for nondestructive evaluation (NDE) of the bond region and for measuring the bond dimensions. (C) 2000 Acoustical Society o f America. [S0001-4966(00)01603-9].