Ta De-an, Liu Zhen-qing, Liu Xiao
Department of Electronic Engineering, Fudan University, Shanghai 200433, PR China.
Ultrasonics. 2006 Dec 22;44 Suppl 1:e1145-50. doi: 10.1016/j.ultras.2006.05.156. Epub 2006 Jun 9.
A novel combined spectral estimate (CSE) method for differentiation and estimation the phase velocities of multimode Lamb waves whose wave numbers are much close or overlap one another in multiplayer plates is presented in this paper, which based on auto-regressive (AR) model and 2-D FFT. Simulated signals in brass plate were processed by 2-D FFT and CSE. And experiments are performed by using two conventional angle probes as emitter and receiver on the same surface of three-layered aluminum/xpoxy/aluminum plates, which include symmetrical and unsymmetrical plates. The multimode Lamb waves are excited in these laminates, and the received signal is processed by 2-D FFT and CSE, respectively. The results showed that the phase velocities of multimode signals whose wave numbers are much closed cannot be differentiated by 2-D FFT, but CSE has strong spatial resolution. Compared the measured phase velocities with the theoretical values, the error is smaller than 2% on the whole. It promises to be a useful method in experimental signals processing of multimode Lamb waves.
本文提出了一种新颖的组合谱估计（CSE）方法，用于在多层板中区分和估计波数非常接近或相互重叠的多模兰姆波的相速度，该方法基于自回归（AR）模型和二维快速傅里叶变换（2-D FFT）。通过二维快速傅里叶变换和组合谱估计对黄铜板中的模拟信号进行了处理。并使用两个传统角度探头作为发射器和接收器，在三层铝/环氧树脂/铝板的同一表面上进行了实验，其中包括对称板和非对称板。在这些层压板中激发多模兰姆波，并分别通过二维快速傅里叶变换和组合谱估计对接收到的信号进行处理。结果表明，二维快速傅里叶变换无法区分波数非常接近的多模信号的相速度，但组合谱估计具有很强的空间分辨率。将测量的相速度与理论值进行比较，整体误差小于2%。它有望成为多模兰姆波实验信号处理中的一种有用方法。
