Research On Deformation Reconstruction For Plate And Shell Structures Based On Strains

The conformal antennas on combat platform develop gradually in the direction of intelligent,large-scale with the increasing demand for information acquisition technology and countermeasure technology in modern war.As the structure of conformal antenna becomes more and more complex and its size increases,its structure is very easy to be affected by the deformation of the aircraft body structure attached to it,which will further affect the performance of the antenna.In order to ensure the normal operation of the conformal antenna,it is necessary to monitor the deformation of the body surface or the structure of the conformal antenna.For the structural deformation monitoring,this thesis studies a technical mean to reconstruct the structural deformation field with strain information and the deformation reconstruction of plate and shell structures based on four-node rectangular element,eight-node shell element and eight-node body element are discussed respectively.Then the theory of this thesis is verified by simulation and experiment.The first part of this thesis introduces the basic framework of the inverse finite element method through simple four node element.And the strain formula of the rectangular element is derived on the basis of the plate theory.The relation matrix from strain field to displacement field is derived by theoretical strain and surface measurement strain of the element.At last a plate model is simulated to verify the accuracy of the proposed method.The next part of this thesis is to expend the category of existing i FEM-based elements on the on the basis of inverse finite element method(i FEM)algorithm.The structural displacement reconstruction methods based on eight nodes shell elements and eight nodes body elements are derived respectively.And the thesis also introduces the concepts of isoparametric element.The application of inverse finite element method is more and more abundant.Then the accuracy of the method is verified by finite element simulation examples.The last part of this thesis is mainly about the physical verification of the methods to verify the engineering value of this method.First of all,the NDI equipment for measuring deformation and the fiber Bragg grating sensor for measuring strain are introduced,the strain measured by the sensor is used to calculate the deformation and compare to the NDI measurement data.The feasibility of the method was verified on the flat plate,curved plate and wing model respectively in order to verify the engineering value of the method.The research method in this thesis has many advantages comparing with those of other structural deformation monitoring technology.The method can evaluate the displacement field of the whole structure using the strain on the surface of the plate and shell structure information and the size of the structure without the load environment.It has a high value for engineering application.This thesis deduces the deformation reconstruction algorithm of various element forms.It can be applied to various complex forms of plate and shell structure.Experiments can also prove that this method is good for the deformation reconstruction of plate and shell structure,and it is an important means and method for structural health monitoring technology.