Chirped Effect Of FBG And Different Temperature Fields Research On Tubular Structure State By Monitoring Technology

Aerospace structures often work in complex environments such as heat,force and magnetism.when the structure is deformed by temperature,the mechanical properties are weakened and the structure will has security risks,so it is necessary to test mechanical properties of the structure.Fiber Bragg grating sensor can detect more than 70 physical quantities such as temperature and strain,and has the advantages of small size,light weight,high sensitivity,anti-electromagnetic interference.it is also easy to build a superior performance of distributed sensor network,which can be used to long distance,high precision and meet the requirement of distributed monitoring.Therefore,this paper studies the monitoring methods of thermal strain and deformation of typical aerospace materials and structural based on optical fiber sensing technology.The main work includes the following aspects:Firstly,according to the requirement of temperature field monitoring in aviation structure,the cause of chirped effect of fiber grating in complex environment temperature field is studied.By using optical simulation software Optigrating,non-uniform temperature and non-uniform strain of fiber grating reflection spectrum is simulated.Then,build test system to obtain the fiber grating reflection spectrum of non-uniform temperature field and strain field,obtaining a reasonable explanation for chirp phenomenon of fiber grating.Secondly,in order to monitor structural states under different temperature fields,the response characteristics of FBG sensors need to be monitored.The sensing characteristics of fiber grating under the condition of different forms and cementation were studied and compared in high and low temperature,further to explain chirp phenomenon.By designing a reasonable packaging sensor,the low temperature chirp effect of fiber grating is eliminated.Thirdly,a temperature field monitoring system of aluminum alloy and carbon fiber composite material based on Distributed Fiber Bragg grating sensor network was constructed to realize the strain deformation monitoring of tubular structure under steady-state uniform temperature field.According to deformation theory and simulation analysis of the structure under uniform temperature,a fast calculation method of axial deformation of the tubular structure,and verify the effective is proposed.Finally,on the basis of previous studies,a distributed fiber optic monitoring system for non-uniform temperature field of tubular structures is developed.According to the simulation results of the surface temperature of Aluminum Alloy tubular structure,field gradient and axial deformation were analyzed.Also the response characteristics of reflection spectrum of fiber grating on the surface of tubular structure is analyzed.