基于时频分析的Lamb波散射源定位方法研究

Research on the Localization Method of Lamb Wave Scattering Source Based on Time-frequency Analysis

针对Lamb波损伤定位中频散效应对定位精度的影响,提出了基于时频曲线和椭圆定位法的Lamb波散射源定位法。利用经验模态分解(EMD)法把散射信号分解成有限个窄带信号分量,再采用改进的连续小波变换(CWT)求出每个信号分量的时频曲线,叠加形成整个信号的时频曲线,实现对不同频率成分波达时刻的准确判别。利用椭圆定位法获得对应于散射信号中一系列频率成分的定位结果,最终由这些多组定位的综合判定损伤位置。在铝板结构上的测试结果表明,在频散较严重的A0模式低频段,该方法求出的时频曲线较细致,损伤位置定位较精确,能有效排除偶然因素对最终结果的影响。

Considering the influence of Lamb wave dispersion on the precision of damage detection,a new detection method of scattering source based on time-frequency curves and ellipse localization method is proposed.Empirical mode decomposition（EMD） is used to decompose the scattering signal into finite narrowband signals,and a modified continuous wavelet transform（CWT） is further used to get the time-frequency distribution（TFD） of the detected signal,and the arriving time of different frequency component is estimated based on TFD.A series of location results can be obtained from different frequency components using ellipse localization method.The damage position can finally be estimated by synthesizing localization results at different frequencies.Experiments on aluminum plate are conducted to demonstrate the efficiency of the proposed method.EMD-CWT analysis can get precise time-frequency curves in highly dispersive low frequency band of A0 mode.The damage location results is more accurate and the influence from occasional factors can be suppressed by using the synthesized method.