Monitoring Method Of Spatial Structure Thermal Deformation And Strain Field Based On Distributed Optical Fiber

Aerospace structures usually operate in complex environments with multiple physical fields.In such extreme environments,structures are vulnerable to the effects of temperature and external forces,which induces changes in structural mechanical properties,resulting in reduced safety and reliability of structures.Therefore,it is of great significance to monitor the thermal deformation and strain field of typical aerospace structures.For this reason,the methods of thermal deformation monitoring and strain monitoring and strain field inversion based on optical fiber sensing technology are studied in this paper,which provide support for real-time monitoring of structural health.The main research work includes the following aspects:Firstly,according to the sensing mechanism of FBG,a kind of FBG strain sensor package based on metal material with strain sensitization characteristics is designed.The strain sensing sensitivity of FBG strain sensor is improved,and the strain measurement error is reduced,which provides technical support for high-precision strain monitoring of aircraft and spacecraft structures.Secondly,a distributed optical fiber on-line monitoring system for thermal strain and thermal deformation of space extension arm structure under uniform thermal load is constructed,aiming at the structural health monitoring under thermal load of space extension arm structure with square bar as unit.A method for calculating the axial thermal deformation of the extension arm structure under uniform thermal load is proposed,and the feasibility of the method is verified.Thirdly,a thermal strain and deformation monitoring system based on distributed optical fiber sensor under non-uniform thermal load is constructed.Two methods of calculating axial thermal deformation based on heat conduction theory and empirical formula of finite element are proposed respectively,and the axial thermal deformation of the structure is obtained.On this basis,the inversion of the axial temperature field and thermal strain field is realized.Finally,according to the requirement of service condition monitoring of space truss structure,the strain field inversion methods of space truss beam structure and front structure are studied respectively.From the point of view of numerical simulation and experiment,the effect of strain field inversion method for beam and plate structures under different boundary conditions is verified,and the applicable conditions of strain field inversion method are given.