基于非线性激光超声的微裂纹检测及定位

Detection and Location of Small Crack Using Nonlinear Laser Ultrasonic

金属构件在加工及服役过程中,其表面及内部会产生微裂纹,外载荷作用下,微裂纹会逐渐扩展,成为影响构件安全运行的重大隐患,因而有必要对构件进行无损检测。提出一种基于非线性激光超声的微裂纹检测技术方法,通过提取激光超声波与微裂纹作用后非线性特征参数的改变量进行裂纹检测及定位。利用激光辐照构件激发超声波,根据构件时域动态响应信号重构状态空间,提出一种非线性特征参数提取方法对裂纹影响下状态空间改变量进行评估以识别裂纹,进而利用扫描激光法实现裂纹定位分析。搭建实验系统对铝合金表面不同宽度微裂纹进行检测,结果表明,所提方法能有效检测并定位构件表面微裂纹。

The produce of small surface and inner cracks is inevitable in metallic structural that is subjected to complex and cyclic loading.The growth of the crack threatens the safety of structure,and may results in serious consequences.It is very important to detect the presence of cracks by non-destructive testing.In this paper,a novel technique for detection and location of small cracks is presented.The metallic structural is radiated by lasers to produce ultrasonic and the state space predictive model is constructed based on the dynamical responses in time domain.A nonlinear damage feature is then extracted from the model to indentify the crack.Furthermore,the crack is located and visualized by using the feature extracted from the entire scanned area.An example of the technique and experimental detection are given for alloys with different cracks.The experimental results show the reliability of the technique.