多模式兰姆波走时提取的希尔伯特黄变换方法

Application of Hilbert-Huang Transform to Arrival Time Extraction of Multi-Mode Lamb Waves

根据希尔伯特黄变换时间分辨率精度较高的优点以及兰姆波信号多模式的特点,将希尔伯特黄变换方法用于兰姆波层析成像中复杂波形到达时间的提取。首先,通过经验模态分解将原始信号分解成固有模态函数,然后对固有模态函数进行希尔伯特变换,以所得波形包络的峰值对应的时间作为多个兰姆波模式的走时。通过与原始信号峰值包络、希尔伯特变换包络和小波变换包络的比较结果表明,希尔伯特黄变换的包络更为平滑,可以准确地提取多模式信息。

According to the advantage of precise time resolution in Hilbert-Huang transform (HHT) and the characteristic of multi-mode Lamb waves, the HHT method was applied to arrival time extraction of complex waveforms in Lamb wave tomograp hy. First, the original signals were decomposed into intrinsic mode functions(IMF) by performing empirical mode decomposition (EMD), then the Hilbert transform was performed to the IMF, and the resulted peak values of the envelope were used as the arrival time of the multiple Lamb wave modes. Comparisons were made among the p eak envelope of the original signal, the direct Hilbert transform (HT) envelope and the wavelet envelope. The results show that the HHT technique provides a smoother en velope and therefore has the capability to extract more accurate arrivals for th e multiple mode Lamb waves.