The transition from Lamb waves to longitudinal waves in plates

We use finite element simulations and experiments to examine the excitation of waves in a plate by normal forces applied to an edge. At low values of the frequency-plate-thickness product, f d, multiple Lamb wave modes are excited with different group velocities, but increasing f d leads to the formation of a train of well-defined nearly longitudinal pulses. We investigate the transition between these two wave types, and for the train of nearly longitudinal pulses we determine the rate at which energy is transferred from the leading pulse to the trailing pulses. Finally, we examine the potential of these longitudinal waves for flaw detection. Experiments and simulations show that the longitudinal pulse train is reflected or transmitted from a slot without significant mode conversion.