Li Zheng, Su Dashuai, Sun Xiaofeng
Appl Opt. 2023 Oct 10;62(29):7571-7576. doi: 10.1364/AO.501760.
The desired narrowband mode of a Lamb wave can be generated efficiently, as long as the laser's moving speed matches the mode's phase velocity, which is a typical characteristic of the moving continuous wave (CW) laser excitation method. In this paper, mode zero group velocity (ZGV) waves can be generated efficiently when the laser's moving speed matches the phase velocity of the mode at the ZGV point, while the two fundamental Lamb modes, i.e., and waves, can be avoided. Meanwhile, measurements on thin plates of stepped thickness were carried out by using the zero-group velocity effect of the mode. Those simulation results demonstrated that the - resonance can be used to measure the thickness of thin plates by tracking the resonance peak as the sample was scanned, and good accuracy can be achieved, since the measurement was reduced to a simple frequency gauging of sample resonances in the ultrasonic domain, which provides a reliable method to measure a thin plate of varying thickness.
只要激光的移动速度与模式的相速度相匹配，就可以高效地产生所需的兰姆波窄带模式，这是移动连续波（CW）激光激发方法的典型特征。在本文中，当激光的移动速度与零群速度（ZGV）点处模式的相速度相匹配时，可以高效地产生零群速度模式波，同时可以避免两个基本的兰姆模式，即A0和S0波。同时，利用A0模式的零群速度效应，对阶梯厚度薄板进行了测量。这些模拟结果表明，通过在扫描样品时跟踪共振峰，A0-S0共振可用于测量薄板厚度，并且可以实现良好的精度，因为该测量简化为超声域中样品共振的简单频率测量，这为测量厚度变化的薄板提供了一种可靠的方法。
