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Volume 126, Issue 2, August 2009
- STRUCTURAL ACOUSTICS AND VIBRATION 
126(2009); http://dx.doi.org/10.1121/1.3167277View Description Hide Description
Guided waves in a free isotropic plate (symmetric and antisymmetric Lamb modes) exhibit a resonant behavior at frequencies where their group velocity vanishes while their phase velocity remains finite. Previous studies of this phenomenon were limited to isotropic materials. In this paper, the optical generation and detection of these zero-group velocity (ZGV) Lamb modes in an anisotropic plate is investigated. With a circular laser source, multiple local resonances were observed on a silicon wafer. Experiments performed with a line source demonstrated that the frequency and the amplitude of these resonances depend on the line orientation. A comparison between experimental and theoretical dispersion curves for waves propagating along the  and  directions of the silicon crystal verified that these resonances occur at the minimum frequency of the and Lamb modes. Simulations indicated that it is possible to deduce the three elastic constants of the plate material with good accuracy from these measurements.