Finite Element Modeling And Dynamic Analysis Of Typical Joint Structure Of Spacecraft

The spacecraft structure will withstand various internal and external load excitations such as vibration,impact and noise during actual use,making its dynamic response extremely complicated.With the rapid improvement of computer computing performance,the use of finite element software for dynamic simulation of actual engineering structures has become one of the important means for engineers to carry out structural dynamic analysis and design.In engineering practice,the establishment of a finite element model that accurately reflects the dynamic characteristics of the actual structure is the basis for the inherent characteristics analysis and response prediction of the structure.However,due to the wide existence of the connection structure in various spacecraft,it has a great impact on the dynamics of the spacecraft.These effects are mainly reflected in the presence of the connection structure that makes the entire structure stiffness lower and has nonlinear characteristics.Therefore,it brings serious challenges to the accurate modeling and dynamic response prediction of the spacecraft structure.How to accurately model the spacecraft connection structure has always been the primary concern of engineers when establishing finite element simulation models.In this paper,the topic of accurate finite element modeling and dynamic analysis of the typical connection structure of the spacecraft is studied.The complexity of the dynamic characteristics of the connection structure lies in the uncertainty of the contact stiffness of the connecting joint surface.Therefore,this paper first analyzes several typical theoretical models of contact stiffness,and studies the influencing factors and variation rules of the contact stiffness of the connecting joint surface.Secondly,modal tests were carried out on the three composite laminate bolt connection structures,and the effect of bolt preload on the dynamic characteristic parameters of the bolt connection structure was studied,and test data was provided for subsequent finite element modeling and simulation.According to the actual engineering needs,the simplified modeling of bolts and the linear equivalent modeling of the stiffness of the fixed contact interface in the bolt connection structure were studied,and the advantages and disadvantages of various modeling methods were analyzed.And based on different modeling methods,the finite element modeling and finite element modal analysis of the composite material bolted structure were carried out.By comparing with the experimental modal results data,the rationality and applicability of various modeling methods were analyzed,which provides a certain reference for the equivalent linear modeling of connecting structures in practical engineering.At the end of this paper,the finite element equivalent modeling of the two typical spacecraft connection structures in the actual aerospace engineering structure is carried out,in which the bolt structure is simplified to the "beam element + MPC" method for simulation,and the contact stiffness between the joint surfaces was equivalent with the virtual material method.In order to obtain an accurate finite element model that can more accurately reflect the dynamic characteristics of the actual structure,a model modification method considering the damping effect is proposed.In order to obtain an accurate finite element model that can more accurately reflect the dynamic characteristics of the actual structure,a finite element model updating method considering the damping effect is proposed.This model updating method uses the idea of step-by-step correction.Based on the modal test data and random vibration response data,the stiffness and damping parameters of the virtual material are updated successively to make the finite element calculation results consistent with the test data.Due to the consideration of the damping effect,this model updating method is very important for improving the accuracy of FEM in practical engineering applications.