Laboratoire Ondes et Acoustique, ESPCI, Université Paris 7, Paris Cedex 05, France.
J Acoust Soc Am. 2011 Aug;130(2):689-94. doi: 10.1121/1.3607417.
The local resonances of a free isotropic elastic plate are investigated using laser ultrasonic techniques. Experimental results are interpreted in terms of zero group velocity Lamb modes and edge mode. At a distance from the edge larger than the plate thickness a sharp resonance is observed at the frequency where the group velocity of the first symmetrical Lamb mode vanishes. Close to the edge of the plate, the resonance due to the edge mode dominates. Both zero group velocity and edge resonances appear at the theoretically predicted frequencies. These frequencies do not vary with the distance from the edge of the plate and the transition between the two modes of vibration, at about the plate thickness, is abrupt. Using a laser excitation on the edge, the amplitude profile of the normal displacement at the edge resonance frequency was determined.
利用激光超声技术研究了各向同性自由弹性板的局域共振。实验结果用零群速度 Lamb 模态和边缘模态进行了解释。在距边缘大于板厚的距离处，在第一对称 Lamb 模态群速度为零的频率处观察到尖锐的共振。在板的边缘附近，由于边缘模态而引起的共振占主导地位。零群速度和边缘共振都出现在理论预测的频率处。这些频率不随距板边缘的距离而变化，两种振动模式之间的过渡，大约在板厚处，是突然的。在边缘处使用激光激励，确定了在边缘共振频率处的法向位移的振幅分布。
