铝板中Lamb波模式识别方法

Research on Methods for Mode Identification of Lamb Waves in Aluminium Plate

介绍利用波速法、二维Fourier变换法和平滑伪Wigner-Ville分布三种方法,对铝板中因频散而产生的多种Lamb波模式进行识别。试验用5 MHz纵波斜入射,分别在厚度为0.82和1.32 mm的铝板中激发出单一模式和多模式Lamb波。结果表明,波速法适合识别单一模式,二维Fourier变换和平滑伪Wigner-Ville分布均可有效识别出多模式Lamb波,并且后者能提供不同模式在时域内的位置信息。实际中二维Fourier变换方法适用于机械自动扫描,平滑伪Wigner-Ville分布则适用于对实时性要求不高的场合。

Three methods were discussed which were wave velocity method, two dimensional Fourier transform method and smooth pseudo Wigner-Ville distribution. The experiments were carried out on aluminium plates, and the single and multimode Lamb waves because of its nature dispersion were excited by 5 MHz oblique incidence longitudinal wave in 0. 82 mm and 1. 32 mm thick plates respectively. The results of these methods showed that wave velocity method was effective for single mode Lamb waves, while the other two methods were able to identify multimode, furthermore, smooth pseudo Wigner-Ville distribution could give the information of position of different Lamb wave modes in time domain. In practice, two-dimensional Fourier transform was suit for automatic scanning, and smooth pseudo Wigner-Ville distribution should be used in the case where there was no real time required.