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A0两个模态多种频率的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A0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。
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 Alumimml 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 SO and A0 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 are located symmetrically respect to the plate. The signals received by each AE transducer are added or subtracted each other, in this way Lamb wave of pure SO or A0 mode are extracted individually. Each mode is then filtered with different frequency. The Lamb wave of single mode with different frequencies makes the signal from an artificial defect clearly displayed.
出处
《应用声学》
CSCD
北大核心
2013年第5期341-347,共7页
Journal of Applied Acoustics
关键词
激光超声
二维傅里叶变换
模态分离
Laser ultrasonic, Two-dimensional Fourier transformation, Mode separation
