Research On Damping Modeling Method Of Astronautic Structures

The dynamic analysis of a typical astronautic structure is carried out in this paper.Focusing on the problem of structural joints modeling,the modeling of bolting damping effect is mainly studied.The thin layer element is used to simulate the bolting of the bracket structure,and the damping of the structure is modeled with the measured frequency response as the design objective.The result shows that the proposed damping modeling method has a reference value for engineering application.The main works in this paper as follows:(1)The application of viscous damping theory,hysteretic damping theory and equivalent viscous damping theory in finite element modeling is discussed.The vibration response with proportional damping or non-proportional damping is studied.And the modeling accuracy as well as the damping matrix assembly and damping additive effects in the finite element are analyzed.(2)The vibration test of the astronautic bracket is designed and conducted.The acceleration response signals of platform and bracket are measured by applying the basic excitation on the shaking table.And then the acceleration transfer rate function is obtained,which is used to identify the modal parameters of the astronautic bracket.Based on the modal parameter identification method,the modal parameters of the vibration frequency and damping ratio are obtained,which provides the experimental data for the subsequent damping modeling.(3)Several common damping modeling methods for astronautic structural joints are discussed,and the modeling method of thin layer is emphatically studied.The modeling principle of thin-layer element and the influence of relevant parameters of thin-layer element on modeling are discussed.Finally,the concrete application of the method in Nastran is given.(4)The finite element modeling of the astronautic bracket is carried out by the thin layer element method studied in this paper.Finite element meshes of the bracket structure are carried out by Hypermesh and Patran,and stiffness of the finite element model is updated by Nastran's optimization and sensitivity analysis.On this basis,two methods are used to model the damping effect respectively.The analysis results show that the natural frequency error of simulation and experiment is less than 5% and the RMS of each frequency band is ? 3dB,which meets the requirement of engineering accuracy.Finally,the finite element modeling validation of a typical spacecraft cabin equipment is completed.