基于模态分析和小波变换的声发射源定位新算法研究

针对传统声发射源定位中，声发射信号到达传感器的时间受设定门槛电压影响很大，导致声发射源定位效果较差，提出了一种声发射源定位新方法。根据模态声发射理论，携带声发射源信息的声发射信号在结构中传播过程中，具有频散现象和多模态特性。因此，声发射源定位应基于同一频率下、同一模态导波到达各个传感器的时间和传播速度。通过对声发射信号进行Gabor小波变换的方法，在时频空间内确定某一频率下某一模态导波到达传感器的时间；并通过数值计算得到该频率处模态导波的群速度，从而实现声发射源的准确定位。通过薄板中声发射线源定位试验，证明了该定位算法的有效性。

A New Acoustic Emission Source Location Technique Based on Wavelet Transform and Mode Analysis

For wave propagation in dispersive media, the arrival time of acoustic emission signal to sensor depended on the setting of threshold voltage, which resulted in the inaccuracy of the acoustic emission location. Based on the wavelet transform and the theory of modal acoustic emission, a new method is proposed to improve the accuracy of acoustic emission source location. It is believed that the acoustic emission signal propagation in the structure has the characteristics of multi|mode and dispersion, and the acoustic emission source location should use the arrival time to sensors obtained from not only the same mode but also on the same frequency in the output signals. The wavelet transform was used to resolve the problem. By utilizing the time|frequency data of the wavelet, the frequency|dependent arrival time traveling was easily obtained; by numerical computation of the wave propagation in structure, the group velocity of the guided mode was also obtained, therefore the accuracy source location was realized. The acoustic emission source location experiments were conducted in a thin steel plate, it is demonstrated the technique is an effective tool for acoustic emission source location.