Réflexion et conversion d'une onde de Lamb à l'extrémité biseautée d'une plaque

This study deals with the Lamb wave interaction on a bevel. The aim is to identify the different reflected modes which exist when a wave is incident on the bevelled end of a plate and to evaluate the respective energy of each mode. In a first time, the study is experimentally realised on a stainless steel plate. Energy balances are performed from the displacement measurements on the surface by laser interferometry. They are corrected to take into account wave diffraction. A theoretical model, based on a modal decomposition, is also done in order to justify the previous results. Computations of the energy reflection coefficients have been realised when the A0, S0 and A1 Lamb modes are incident on plate ends bevelled from 65 to 90°, for a frequency-thickness product included between 1 and 4 MHz mm. The quantitative balances obtained by this method agree with the experimental results. The theoretical computation reveals the importance of “complex modes” at the plate extremity. A finite element simulation confirms their effect on the reflections and allows to evaluate the distance from the bevel where the reflected Lamb waves are alone. Finally, a study is done to know the influence of a bevel on the “edge mode” behaviour - the “edge mode” is a particular phenomenon which appears in a narrow frequency band when the S0 Lamb mode is incident.