Research On Deformation Monitoring And Strain Field Reconstruction Based On Distributed Optical Fiber Sensor

Aerospace structures are vulnerable to damage due to bad environment during long-term service,which leads to the decline of safety performance of aircraft.Deformation and strain information is an important basis for evaluating the structural health of aircraft.Therefore,the deployment of deformation monitoring and strain field reconstruction for aircraft structures is of great significance.For this reason,this paper presents a technology of structural deformation monitoring and strain field reconstruction based on distributed fiber Bragg grating sensors,which can improve the ability of structural health monitoring of aircraft and ensure the safety and reliability of aircraft during service.The main research work of this paper includes the following aspects:Firstly,aiming at the characteristics of large aspect ratio tubular structures similar to launch vehicle shells,the deformation algorithms based on coordinate transformation principle and the deformation algorithms based on tangent recurrence principle are studied respectively.Using ANSYS numerical simulation method,the feasibility of the two deformation algorithms is verified.Secondly,a large aspect ratio tubular structure deformation monitoring system based on distributed fiber Bragg grating sensor is constructed,and a visualization program of tubular structure deformation monitoring based on graphical software LabVIEW is developed.By comparing the resurfacing deformation of distributed optical fiber deformation monitoring system and the displacement directly measured by laser displacement sensor,the feasibility of the two deformation algorithms is verified by experiments,and the influencing factors of reconstruction error are given.Thirdly,aiming at the requirement of wing structure deformation monitoring,the deformation monitoring algorithm based on modal superposition principle is studied.The strain and displacement modes of aluminium alloy plate were analyzed by finite element method.On this basis,a deformation monitoring system for unilateral clamped aluminium alloy plate based on FBG sensor is constructed.The displacement field of aluminium alloy plate is reconstructed according to the strain information in the key area of the structure measured by the fiber and the transformation relationship between the displacement and strain of the structure.Finally,a strain field reconstruction algorithm for flexible thin plate structures based on modal superposition principle is proposed.The feasibility of applying the algorithm to unilateral clamped aluminium alloy plate and quadrilateral clamped composite plate is verified by numerical simulation.A strain field reconstruction system of aluminum alloy sheet based on distributed optical fiber is constructed,and the strain field reconstruction of aluminum alloy sheet under different loading modes is realized.