基于模态识别与分离的铝板激光超声检测-应用声学.PDF

第32 卷 第5 期 Vol.32, No.5 2013 年9 月 Applied Acoustics Sept., 2013 基于模态识别与分离的铝板激光超声检测 † 戈 浩 蔡桂喜 刘 畅 董瑞琪 （中国科学院金属研究所 沈阳 110016 ） 摘要 用Nd:YAG 激光器在2 mm 厚的铝板上激发激光超声，通过激光反射镜偏转进行点阵扫描激励，用声发射 传感器接收在铝板中传播的激光超声信号，通过信号放大和数据采集得到激光超声在铝板中传播的数据。对上述 数据进行二维傅里叶变换得到了铝板中激光超声的模态分布和频率分布，接收到的激光超声是S0 和A 0 两个模态 多种频率的Lamb 波。利用两个相同的探头对称地压紧在板的两个表面上，对两个探头接收到的信号进行相加和 相减，可以将S0 和A 0 模态分别提取出来。对单一模态的Lamb 波再进行滤波，得到了窄频带单一模态的Lamb 波。采用该方法实现了从杂乱的激光超声原始信号中提取出清晰的伤信号，并且得到了不同模态在不同频率范围 的检测结果。 关键词 激光超声，二维傅里叶变换，模态分离 中图分类号：TB553 文献标识码：A 文章编号：1000-310X(2013)05-0341-07 Laser ultrasonic detection of flaw in aluminum plate based on modes identification and separation GE Hao CAI Guixi LIU Chang DONG Ruiqi (Institute of Metal Research , Chinese Academy of Sciences , Shenyang 110016) Abstract A Q-switched Nd: YAG pulsed laser fires laser pulses to the laser mirror scanner (LMS), the LMS maneuvered the laser pulses for a 2 mm thick Aluminum plate. The laser ultrasonic waves caused by every laser impinging point are received by an acoustic emission transducer(AE), then amplified and digitalized by an oscilloscope. The two dimensional Fourier transformation of the received signals shows that the wave received by the AE transducer is composed mainly of Lamb waves of S0 and A 0 modes which have a range of frequencies. Two AE transducers of the same characteristics are pressed on the plate’s opposite surfaces respectively and they