激光导波阵列波束成形损伤成像方法

Array beamforming and damage imaging based on laser guided wave

激光超声检测方法在结构损伤检测领域有着广泛应用。增加激光信号用于损伤成像的技术难点。针对此挑战,采用提出的Morlet小波分析法提取激光宽频信号中对应中心频率下的窄带信息。为实现损伤的可视化,分析比较了导波阵列波束成形损伤成像算法中时间延迟叠加算法和相位延迟叠加算法,其中相位延迟叠加成像法对频域内所有频率成分实施延迟叠加能克服导波的频散效应得影响,能实现对损伤更精确的定位。为验证该方法的实用性,构建了激光激励/接收完全非接触式的实验系统,通过对Morlet小波分析后的信号采用延迟叠加算法对损伤进行成像,实验结果表明了:相位延迟叠加成像法成像效果比时间延迟成像法成像效果更佳,定位更精确。

The detection method based on laser ultrasonic wave has a broad application in the field of structural damage detection.but the laser signal has the characteristics of a wide-frequency band,which makes the incident signals and the damage sacttered signals severely difficult to be effectively separated in the time domain,resulting in the failure to extract the damage scattered signal information.For this challenge,the Morlet wavelet analysis was proposed to extract the nanowband information at the corresponding center frequency in the laser broadband signal.To visualize damage and to locate damage more accurately,time delay-and-sum algorithm and phase delay-and-sum algorithm in the guided wave array beamforming and damage imaging were analyzed and compared,the time delay imaging technology only implements delay-and-sum in the time domain,which cannot avoid the dispersion effect of guided wave.However,phase delay imaging technology thinkds of all the frequency components which overcomes the dispersion effect,and enable more accurate damage location.In order to verify the practicability of this method,a completely non-contact experimental system for laser excitation/reception was constructed.The signal after Morlet wavelet analysis was used ot image the damage by using delay-and-sum algorithm better imaging and more accurate position by phase delay-and-sum.