Analysis On Dynamic Characteristics Of Structures With Random Fields Under Thermal-Structural Coupling

Space structure design lays the foundationis for the stable and reliable operation of spacecraft,whereby the prominent problem focus on how to quantify the influence of thermal radiation on structural vibration.Therefore,it is of great significance to analyze the dynamic response of structures in the frame of multifield cuoupling such as temperature field and structural displacement field in the engineering.In this work,the flat plate structure commonly used in spacecraft is taken as the research object,and the thermal deformation is caused by the thermal stress generated by the solar radiation,which is considered in this work.The structural deformation changes the received solar thermal flow into alternating heat flow,which further affects the thermal deformation of the structure.The interaction between the heat and the structure is regarded as the thermal structure coupling.Therefore,considering the randomness of some physical parameters of the structure,the stochastic dynamic response of the spatial random plate structure under the thermal structural coupling is addressd.The specific work is as follows:(1)According to a large number of literatures at home and abroad,the sudden change of"shadow light" of space structure will lead to the thermal vibration and the thermal structure coupling phenomenon,and the randomness of structural physical parameters greatly affects the structural dynamic responses;the research status and progress of some related theories to be used in this work,such as random field,thermodynamics,structural dynamics and the isogeometric analysis method are reviewed.(2)Based on the theory of Mindlin plate,the finite element model of space structure under thermal structural coupling is established and analyzed.The specific process is as follows:1.The plate structure is meshed with finite element,and the dynamic differential equations are obtained by applying mechanical control equations and boundary conditions;2.The structural finite element mesh is expanded to the finite element mesh of heat conduction;3.the differential equations of heat conduction and structural dynamics are expanded by time difference method and Newmark-β method respectively in time domain,and then the temperature field and structural displacement response are alternately iterated and calculated to obtain the temperature response and displacement response at each moment.The analysis via an example shows that the structural vibration will be induced when the spatial plate structure undergoes the "shadow light" cyclic load,and then the vibration amplitude gradually decreases and the vibration tends to be gentle until it is stable.Then,considering the structural elastic modulus and mass density of the structure as random field variables,the Karhunen Loeve method is used to expand them,and the finite element model of stochastic thermal-structural coupling is constructed.The influence of each random field parameter on the structural dynamic response eigenvalue is calculated and analyzed through the example sampling.(3)Based on the non-uniform rational B-spline geometry model of the plate structure,the heat conduction differential equation and dynamic differential equation are derived by using the isogeometric analysis method.The plate is analyzed with CAE directly based on its CAD model,and the model is further refined.When taking the material elastic modulus and mass density as random field variables,the random isogeometry model of thermal-structural coupling for the flat plate structure is constructed,and the temperature field and structural displacement field are then obtained by solving differential equations and the results of isogeometric analysis are compared with those of the finite element analysis so as to verify the effectiveness of the model.Finally,the random field parameters are sampled and analyzed to obtain the influence of different random field parameters on the structural dynamic response,and the results display that the standard deviation of elastic modulus has the greatest influence on dynamic responses.