基于光纤光栅变形光谱的疲劳裂纹扩展监测方法

为研究金属疲劳裂纹扩展的在线监测技术，基于改进传输矩阵的光谱模拟方法，建立反映光纤布拉格光栅（FBG）光谱变形机理的裂纹扩展在线监测方法。研制了疲劳裂纹扩展在线监测系统平台，提出基于平移不变量小波法的试验光谱去噪方法，解决试验光谱信号中非连续与快速变化点难以平滑的问题；提出仅与裂纹扩展状态相关的FBG光谱面积参数，克服了光谱中心波长、光谱带宽等传统特征参数仅适用于恒定外载与恒定温度或对裂纹不敏感的局限性，给出基于光谱面积曲线拐点的裂纹扩展状态判定依据。

Monitoring Approach of Fatigue Crack Propagation Based on Deformation Spectrum of Fiber Grating

In order to study the on-line monitoring technique for metal fatigue crack propagation, in this paper, 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.