Deformation Monitoring Method And Experimental Study Of Aluminum Alloy Plate Structure Based On FBG Sensor Network

Aluminum alloy plate structure is typical structure widely used in the field of aerospace equipment manufacturing.It has the advantages of light material,high specific strength,corrosion resistance,good processing and forming.However,the aluminum alloy plate structure is prone to deformation and even failure due to long-term alternating load and foreign body impact in the service process,which seriously affects the safety and service life of aerospace and spacecraft.Therefore,it is of great significance to monitor the shape change of plate structure in real time and respond to it in time.Fiber Bragg grating(FBG)sensors have the advantages of small size,light weight,corrosion resistance and quasi-distributed sensor network,which has become an important information acquisition technology in the field of structural health monitoring.In this paper,based on FBG sensing technology,a threedimensional shape sensing and reconstruction technology of plate structure is proposed to realize real-time strain sensing and deformation monitoring of aluminum alloy plate structure.The research contents of this paper mainly include the following aspects.(1)Research on the principle and method of plate structure space 3D shape reconstruction.Firstly,the mapping relationship between curvature and strain is studied,and the discrete curvature information is obtained from the strain information of the structure surface.Then bicubic plane interpolation method is proposed to obtain continuous curvature information from finite discrete curvature information.Finally,the coordinate transformation theory is studied.The structure three-dimensional space shape reconstruction algorithm based on orthogonal curvature and coordinate transformation is proposed for the simulated satellite bulkhead plate structure.The cylindrical and hill surface simulation models are constructed,and simulation experiments are carried out.Experimental results show that the spatial reconstruction algorithm based on bicubic interpolation and coordinate transformation can predict structural deformation well.(2)Research on fiber grating strain sensing technology and sensor network optimal layout.Firstly,the FBG sensing theory and fiber grating multiplexing technique applied to structural strain detection are discussed.According to the basic parameters of FBG sensor and the technical specifications of FBG demodulation device,the configuration of fiber optic sensor network is studied.Then,the Abaqus software was used for finite element analysis of the aluminum alloy four-sided plate structure,and the strain distributions and displacement distributions of low order modes were obtained.Based on the mode superposition method,the overall strain distribution of the structure was obtained.Finally,the objective function of optimal sensor layout is constructed according to the characteristics of the reconstruction algorithm and the overall modal information.Based on particle swarm optimization algorithm,the optimal sensor layout scheme is simulated.Compared with the average sensor distribution scheme,the proposed optimal sensor layout scheme has good performance.(3)Design and construction of simulated satellite bulkhead structural deformation monitoring system based on FBG sensor network.Firstly,the hardware platform design and construction of the experimental system were carried out,including the configuration and installation of FBG sensors array,the distribution design of checking points array,the design of motor loading position,and the construction of wavelength demodulation system.Then,aiming at the functional requirements of system software,software modules such as structural information acquisition module,deformation reconstruction algorithm module and user visual interface module are developed by using LabVIEW and MATLAB to realize the visualization of plate structure deformation shape.(4)Simulation satellite bulkhead structural deformation monitoring experiment.Firstly,the experimental flow and loading conditions are designed.Then,several experiments were carried out under different loading conditions to collect the structural strain information,and the structural deformation surface was reconstructed using the proposed spatial reconstruction algorithm.The error of reconstruction algorithm is analyzed by comparing the real displacement value and reconstruction value of structural deformation.The results show that the sensors layout optimization scheme based on particle swarm optimization algorithm is effective.and the proposed spatial reconstruction algorithm based on bicubic interpolation and coordinate transformation can accurately reconstruct the structural deformation surface.For four-sides fixed aluminum alloy structure deformation monitoring requirements,the paper designed the FBG sensors optimization layout method based on particle swarm intelligence algorithm.Based on the bicubic interpolation method and the coordinate transform method,a three-dimensional space reconstruction algorithm is proposed to realize strain sensing and deformation reconstruction of plate structure,which has a good prospect of engineering application.