Research On Deformation Reconstruction Of Plate And Beam Structure Based On IFEM

Structure Health Monitoring(SHM)is a very important discipline in the fields of civil,aerospace,and marine engineering.The use of a ship’s structural health monitoring system can reduce ship maintenance and overhaul costs,while improving crews and the environment safety.The key component of the structural health monitoring system is to use strain sensors and the measured strain information to reconstruct the three-dimensional displacement and stress field of the structure in real time.The strain-based inverse Finite Element Method(i FEM)is a revolutionary deformation reconstruction method that does not require material properties and loading conditions of the structure can restructure the structural deformation in real time,providing a solution for real-time ship structural health monitoring.First,the theoretical section strain is derived based on the Timosheko beam theory,and the least square function of the theoretical section strain and the actual section strain is established,then the relationship between strain and displacement is derived.The simulation of the cantilever beam and the fixed beam verifies the accuracy of the inverse finite element algorithm.By comparing the reconstructed displacement with the displacement obtained from the finite element analysis,it is found that the agreement is good,which proves the accuracy of the beam inverse finite element algorithm.On this basis,the applicability of the inverse finite element method to the reconstruction deformation of complex frame structures is discussed,and the accuracy of the inverse finite element method in the reconstruction of complex frame structures is verified through the simulation of the horizontal and vertical frame structures.Then,based on the Mindlin-Ressiner medium-thickness plate theory,the theoretical formula of the surface strain is derived,and the strain is divided into membrance strain,bending strain and transverse shear strain,which are respectively multiplied by corresponding weights for coupling,and by minimizing the functional of theoretical strain and actual strain,establishes the relationship between strain and displacement,and deduces the inverse finite element mathematical model of the four-node plate.The simulation of the cantilever plate verifies the accuracy of the inverse finite element method.Finally,through the design and construction of a cantilever beam experimental platform,a centralized loading experiment was carried out,and the reconstruction accuracy of different measuring point schemes was compared and analyzed,and the source of the experimental error and its influence were analyzed.The results showed that the axial angular position deviation was the main source of experimental error,the accuracy of the reconstruction results can be improved by increasing the signal-to-noise ratio in the experiment.Through the design and construction of a four-sided fixed-supported flat plate experiment platform,the uniform loading experiment was carried out,and the surface strain information collected by the strain measurement system was used to reconstruct the structural deformation,and compared with the displacement information obtained by the displacement measurement system,which verified the accuracy of the inverse finite element method for plate structures in practical application.