基于小波谱白化与自适应小波重构的木材损伤声发射源直线定位法研究

Linear Positioning Method of Acoustic Emission Source of Wood Fracture Based on Wavelet Spectral Whitening and Adaptive Wavelet Reconstruction

针对木材断裂声发射(acoustic emission,AE)信号源定位问题,提出了一种基于小波谱白化与信号相关性分析的木材表面AE源直线定位算法。首先,为得到木材断裂时产生的AE信号,使用万能力学试验机进行三点弯曲加载试验,在试件表面相距固定距离的3个位置采集试件断裂时产生的AE信号,设置采样率为500 kHz。然后,为合理补偿AE信号在传播过程中损失的高频部分提升信号分辨率,提出一种小波谱白化算法。为降低噪声信号的影响,提出了一种自适应的小波重构算法。最后,通过信号相关性分析法,计算信号到达各传感器的传播时差,并采用基于时差直线定位算法进行AE源定位。结果表明,木材断裂过程中,AE信号通过木材表面和木材内部2种途径传播,由于传播介质不同造成不同的传播速度。使用原始、小波谱白化重构、自适应小波重构的3种AE信号进行AE源定位时,木材表面AE源的定位误差为11.3%、2.6%、3.7%,木材内部AE源的定位误差为10.7%、2.9%、4.5%。AE信号的重构算法直接影响基于时差的AE源定位算法精度,特别是使用小波谱白化法能够显著提升AE信号分辨率同时提升计算时差的准确性进而提升AE源定位精度。

Aiming at the issue of localization of acoustic fracture(AE)signal source of wood,a linear positioning algorithm of AE source based on wavelet whitening and signal correlation analysis was proposed.First,in order to obtain the AE signal,the study used a universal testing machine to perform the three-point bending load test,collecting the AE signal generated when the test piece breaks at three positions at a fixed distance from the surface of the test piece and set the sampling rate to 500 kHz.Then,in order to reasonably compensate the high-frequency part of the loss of the AE signal during the propagation process and improve the signal resolution,a wavelet spectrum whitening algorithm was proposed.In order to reduce the influence of noise signals,an adaptive wavelet reconstruction algorithm was proposed.Finally,through the signal correlation analysis method,the propagation time difference of the signal reaching each sensor was calculated,and the AE source positioning was carried out by using the time difference linear positioning algorithm.The experimental results showed that during the process of wood fracture,the AE signal propagated through the wood surface and the interior of the wood.Due to the different propagation media,different propagation speeds were resulted When using three kinds of AE signals of original,wavelet spectrum whitening reconstruction and adaptive wavelet reconstruction to locate the AE source,the positioning results of the AE source on the wood surface were 11.3%,2.6%,and 3.7%,and the positioning results of the AE source inside the wood were 10.7%,2.9%,4.5%,respectively.The reconstruction algorithm of the AE signal directly affects the accuracy of the AE source positioning algorithm based on the time difference.In particular,the use of the wavelet spectrum whitening method can significantly improve the resolution of the AE signal and the accuracy of the calculated time difference,thereby improving the AE source positioning accuracy.