基于小波变换时频能量分析技术的岩石声发射信号时延估计

声发射源定位技术是根据各传感器接收声发射信号的时差来实现损伤定位的,时延估计精确程度直接影响声发射源定位的精度。首先,在对不同损伤的声发射波形模式和频率识别的基础上,利用小波变换提取相应的单一频率或某一很窄频率段内的波形,并据此实现不同传感器在该频段的时延估计,为声发射源定位提供一个更为科学的方法;然后,使用Hyperion超声波系统,对单轴加载条件下岩石破裂过程中的声发射信号进行监测,并使用仪器自带的定位算法实现声发射源定位;最后,基于小波变换的方法对岩石试样声发射信号的时频能量分布特征进行分析,实现声发射源定位,并将定位结果与试样的真实破裂模式进行比较。试验结果表明,基于小波变换时频能量分析技术有利于减小声发射源定位的误差,从而提高材料损伤定位的精度。

TIME-DELAY ESTIMATION OF ACOUSTIC EMISSION SIGNALS OF ROCK USING TIME-FREQUENCY ENERGY ANALYSIS BASED ON WAVELET TRANSFORM

Since acoustic emission(AE) source location is based on the time delays of AE signals received at each sensor，the accuracy of AE source location is directly affected by the time-delay estimation of AE signals. First，based on the recognition of the waveform and frequency of AE signals using wavelet transform；the waveforms with a single(or very narrow band) frequency，which are related to AE wave with different damages，are extracted and used to estimate the time delays of the AE signals among sensors；thus a more scientific method for AE source location based on wavelet transform is established. Then，the AE signals during the failure process of rock specimen under uniaxial compression are monitored by using Hyperion AE system，and the AE sources are located by using the common arithmetic provided by this AE system. Finally，the wavelet transform-based method is employed to locate the AE source based on the time delays of AE signals estimated according to the time-frequency energy analyses of AE signals. Comparisons between this new AE source location results with those obtained from Hyperion AE system indicate that the errors of AE source location can be effectively diminished；thus it can enhance the precision for damage detection in rocks.