圆柱类金属构件表面裂纹的激光超声识别方法研究

Laser ultrasonic identification method for surface cracks on cylindrical metal components

为了利用激光超声技术有效地识别圆柱表面裂纹,提出利用圆柱表面波信号增强和小波包-奇异值分解(WPT-SVD)方法识别圆柱类金属构件表面裂纹的位置和深度。建立了圆柱的激光超声显式有限元模型,分析了圆柱表面裂纹对表面波的模式转化作用。利用圆柱表面裂纹在激发源位置附近时激光超声扫描信号增强的现象,识别圆柱表面裂纹的位置。在已识别圆柱表面裂纹位置的基础上,通过分析圆柱表面裂纹检测信号的时频特点,利用WPT-SVD提取圆柱表面信号的时频特征,定义参数k r表征裂纹深度的变化,识别圆柱表面裂纹深度。搭建了激光超声圆柱表面裂纹检测实验系统,开展了实验研究,实验结果表明所提出的圆柱表面信号增强和WPT-SVD方法可以识别出圆柱表面裂纹的位置和深度。

Here,in order to effectively identify cylindrical surface cracks with laser ultrasonic technique,a method of cylindrical surface wave signal enhancement and wavelet packet-singular value decomposition(WPT-SVD)was proposed to identify location and depth of surface cracks on cylindrical metal components.A laser ultrasonic explicit finite element model for a cylinder was established to analyze effects of cylindrical surface cracks on mode transformation of surface waves.The position of a cylindrical surface crack was identified using the phenomenon of laser ultrasonic scanning signal being enhanced during cylindrical surface crack being near excitation source.After crack location was identified,time-frequency characteristics of crack detection signal were analyzed,and these time-frequency characteristics were extracted using WPT-SVD.The parameter kr was defined to characterize crack depth change,and cylindrical surface crack depth was identified.Here,a laser ultrasonic cylindrical surface crack detection test system was built to conduct test study.The test results showed that the proposed method of cylindrical surface wave signal enhancement and WPT-SVD can be used to identify position and depth of cylindrical surface cracks.