基于光纤光栅变形光谱的疲劳裂纹扩展监测方法

In order to study the on-line monitoring technique for metal fatigue crack propagation, a crack propagation real-time monitoring method reflecting mechanism of spectrum distortion of the Fiber Bragg Grating (FBG) was established based on the spectrum simulation with improved transmission matrix. The fatigue crack propagation real-time monitoring system was developed independently, and the experimental spectrum denoising method based on translation invariant wavelet method was proposed to overcome the difficulty of smoothing the non-continuous and fast changing points in received test spectrum signal. Further, the FBG spectrum area parameter only related to the crack growth state was proposed, which breaks the limitation that the traditional characteristic parameters such as spectrum center wavelength and spectrum bandwidth are only applicable to constant external load and constant temperature or insensitive to crack. Finally, the judgment method of crack propagation state based on the inflection point of spectrum area curve was developed.