基于状态空间特征提取的微裂纹定量检测

非线性超声法对机械结构微裂纹检测的敏感性与有效性较好,但传统非线性超声法一般不能实现微裂纹定量检测。针对此问题,提出一种针对微裂纹的定量检测方法,通过提取裂纹引发的构件状态空间改变量以对裂纹进行识别、定量检测。该方法采用激光束与待测构件相互作用激发超声波,对其时域响应信号重构表征构件动态特性的状态空间,提取非线性特征参数巴氏距离(bhattacharyya distance,简称BD)对状态空间变量进行分析以对裂纹进行识别,进而利用扫描法实现裂纹的定量检测。通过对铝合金表面不同类型微裂纹的检测实验,验证了该方法对构件表面微裂纹定量检测的有效性。

Quantitative Detection of Small Crack by Nonlinear Laser Ultrasonics

The sensitivity of nonlinear ultrasonic features to small crack is recognized much higher than what can be achieved by conventional linear features. However, in most of cases, the conventional nonlinear ultrasonic features can only locate the crack but difficult to quantify. In this paper, a novel technique for the quantification detection of small crack is presented. The structure needing to be detected is radiated by laser to produce a nonlinear ultrasound and its state space predictive model is constructed based on its dynamical responses in time domain. Then the Bhattacharyya Distance is adopted as the quantification metric to detect the crack. Furthermore, the crack is quantified using the feature extracted from the entire scanned area. An example of the approach and experimental measurement is given for alloys with different kinds of cracks. The experimental results show the reliability of the approach.