Research On The Impact Monitoring Of Typical Aviation Structures Using Fiber Bragg Grating

Aircraft structures are always suffered from impact,fatigue and other loads during the service,manufacturing,transportation and maintenance,resulting in invisible internal damage.The damage accumulates and threatens the structure reliability.Optical fiber has advantages of small size,light weight,corrosion resistance,and distributed networking ability,which is suitable for building intelligent material structure and monitoring the health status of aircraft structure in complex environment.Most of the existing research on impact monitoring technology focused on plate structure,and impact monitoring research for other structures is less.Because of the different characteristics of impact signal of different structures,the transplantation of impact localization method between different structures is not satisfactory,and also causes the waste of workload and calculation.This paper proposed several impact localization methods for different structures by studying the signal of impact on different typical aviation structures,these methods are feasible,can meet the need of practical engineering,reduce the operation complexity and cost of aviation structure maintenance.Finally,by using fiber Bragg gratings(FBG),the monitoring of fatigue crack growth which is also a serious threat to the safety of structures is investigated.The main research work includes:(1)An impact localization method based on detrended fluctuation analysis and centroid localization for composite plate is proposed.The Hurst exponent of impact signal is extracted by the method of detrend fluctuation analysis,and distance estimation model of different directions for each sensor are established to estimate the distance from the impact to each sensor,and the coordinates of the impact are determined by the centroid localization algorithm.(2)An impact localization method based on teager energy operator and wavelet analysis for unilateral clamped wing shaped plate is investigated.Teager energy operator and wavelet analysis are used to extract the swing amplitude of impact signal,and by comparing the swing amplitude of the unknown impact and impact samples,the impact location is acquired.(3)An impact localization method based on wavelet analysis and multi-kernel support vector regression machine for composite barrel structure is proposed.The wavelet packet is used to extract the low frequency node energy of impact signal and put into the multi-kernel support vector regression machine to establish impact location identification models and realize the localization of impact on composite barrel structure.(4)the methods of detrended fluctuation analysis,teager energy operator and wavelet packet analysis are applied to analyze the impact signal of composite stiffened panel and flexible extension structure.The relationship between the hurst exponent and the location of impact on the skin,on the flange of stiffener and on the stiffener were studied,and the sensitivity of different nodes’ energy of impact on the flexible extension structure are also investigated.(5)an on-line fatigue crack monitoring method based on equal dimension and new information grey system is proposed.In the process of crack growth,the response signal of FBG is processed by Hodrick Prescott(HP)filter to extract the signal feature,and the fatigue crack on-line monitoring is realized by using the equal dimension and new information discrete grey model.