Research On Nonlinear Mechanical Behavior Of Connection Structures In Space Vehicle

As a large-scale industrial equipment involving high-end technique,space vehicle has been playing a more and more critical role in modern space engineering.During the whole life span of space vehicle from manufacturing to accomplishing its mission,it will be subjected to all kinds of complex mechanical environment such as vibration,impact,noise,acceleration and microgravity,etc.In order to ensure its regular work,it's significant to design its mechanical characteristics,especially its structural dynamic parameters.Space vehicle is a representative example of connection structures.Thus structural design of it should take the nonlinear mechanics of connection structures into consideration adequately.Therefore,in this dissertation the modelling of connection structures and their nonlinear static,dynamic characteristics are studied to provide a reference for designing space vehicle reasonably.The main work of this dissertation is listed as follows:(1)The multi-connected structures utilized to study the structural dynamic behavior of space vehicle are firstly designed and their fine FEA model involving many nonlinear factors such as friction,contact,clearance and pretension is established.After that,static experiments of connection structures are completed and Finite Element Analysis is conducted to obtain the connection stiffness by axial tension and compression.The nonlinear characteristic of difference between tensile stiffness and compressed stiffness can be apparently observed in the axial force-deformation curves from experiments.In addition,the validity of FEA model is confirmed.(2)The nonlinear static characteristics of bolted-flange connection structures are studied and the Lever effect and Ring effect are elaborated.The pure hex FEA model including screw thread is used to analyze the effect of pretension,bolt length,flange thickness,position of bolt and ribs on Lever effect and Ring effect.(3)A modification of Neuber's rule and ESED method is proposed aimed at the limitation that both original methods are only suitable for predicting elastic-plastic stress concentration of notches in the state of local yielding.The modified ESED method is applied to forecasting the elastic-plastic behavior of bolt with screw thread under typical loading and it gives a better prediction that the original one.(4)The simplified dynamic model including nonlinear connection stiffness is set up.Then the transient dynamic behavior of multi-connected structures in space vehicle is studied based on fine FEA model and simplified dynamic model.The acceleration response results of multi-connected structures show that the transverse impact subjected to structures will bring about coupling vibration of transverse and longitudinal orientation.In addition,the internal force response results bring the change law of internal force to light.It also indicates that the simplified dynamic model lacks the mechanism that depicts the process of contact-friction-slippage,which points out a direction for follow-up work.