Modelling elastic wave propagation in thin plates

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This chapter presents an analysis of elastic wave propagation in thin plates, based on the theory of Viktorov. It illustrates that at the frequency range of interest and for modest plate thicknesses, the only waves that can be excited and propagate in the structure are guided waves (also called Lamb waves). The elastic properties of the panel and the finger touch signature are usually unknown. Therefore, the chapter proposes two different methods for estimating them through simple experimental procedures (calibration). The first is an active method based on the use of a transducer, while the second one is a passive original method, which infers the elastic properties of the board from the information given by a single tactile interaction. The obtained estimates are then used to simulate the propagation in the boards. The approach is to implement the general solution of the elastic wave equation for infinite plates, and introduce the boundary conditions afterwards using a real-time beam tracer. Finally, the chapter illustrates the effectiveness of the approach by comparing the predicted response of a finger touch with the measured one on a medium density fiberboard (MDF) plate, showing how the active and the passive calibration procedures give comparable results.