Investigation On Prediction Methods And Simulation Technniques Of Pyroshock For Complex Satellite Structure

Pyroshock environment of satellite-rocket separation refers to the responses of satellite structures during the process of satellite-rocket separation,which is caused by the actions of pyrotechnic devices.This pyroshock environment,which has the properties of transient,high frequency and high amplitude,has little effect on the main structure of the satellite,while it will case the damages of the precision equipment or the component on board,resulting in the serious consequences.Therefore,these precision equipment and component will undergo the shock test for the shock resistance before launching.However,the accurate prediction and rapid simulation of the pyroshock environment of satellite-rocket separation are still the most difficult problems in aerospace engineering.Under this background,it is of great significant to develop the researches on the accurate prediction methods of pyroshock environment and the simulation techniques for the satellite structure design,acquirement of test condition and rapid realization of the test condition.In this paper,the researches mainly focus on the precise prediction methods by a complex satellite structure and rapid simulation of pyroshock environment for the satellite-rocket separation.Firstly,the Finite Element(FE)model of the pyroshock source,namely the pyrotechniques separation nuts,is established and verified through the near-field pyroshock experiment.The Hydrocode program is used to solve the FE model above,simulating the whole separation process of the pyrotechnic separation nuts.At the same time,the research points out that the explosive shock and strain energy release shock are the two parts of the pyroshock.From the analysis of the responses of the measuring point,the coupling relationships between the explosive shock and the strain energy release shock are revealed.It is shown that there is an obvious order about them in time domain and the envelope of the two sources equals to the ones of the pyroshock in the frequency domain of Shock Response Spectrum(SRS).Secondly,the explicit dynamic code LS-DYNA is used to build and solve the FE model of the middle-field structures,extracting the interface force between the satellite and rocket.The research find this interface force could not replace the shock actions of the near-field pyroshock source to the far-field structures.Therefore,a simple satellite structure is introduced and solved with the numerical method.The transfer characteristics of the shock waves are analyzed and find that these forces at the interfaces of the satellite joint and its adjacent connection beams have the ability to represent the shock actions of near-field pyroshock to far-field structure.These interface forces are further simplified and a reasonable interface is obtained.This research of the extracting method of the interface force combines the researches of near-field pyroshcok source and prediction of the far-field response together,and plays an important role in linking the up and down.Thirdly,this paper break through the problems that the complex satellite cannot be established as FE model or SEA(Statistical Energy Analysis)model uniformly since the dynamic differences among the subsystems of complex satellite structure.A new method for pyroshock environment prediction of complex satellite,namely FE-SEA-VMSS,is presented by combining the FE,SEA and VMSS(Virtual Mode Synthesis and Simulation)methods.The corresponding theories are deduced.The FE-SEA hybrid model of complex satellite is established and solved.Combining the numerical results of the FE-SEA hybrid model and the interface force above,the pyroshock responses of the bottom board and the side board of the propulsion cabin of the complex satellite are calculated with the VMSS method.Through the separation experiment of the whole satellite,the accuracy of the results and the reliability of the method presented above are verified.Finally,a set-up for the pyroshock environment simulation,containing multiple adjustable parameters,is designed based on the mechanical impact model.And then the influence rules of these adjustable paramenters,such as the pressure of the chamber of the light gas gun,position holes of the connection bars,thickness of the loading board and the rubber mat,on the shock environment of the resonant board are researched by the experimental and numerical methods.The quantitative relationship between the adjustable parameters and the three factors of the SRS(slope at low frequency,knee frequency,and amplitude at high frequency)is analyzed and fitted.And these relationships are verified through a typical example.The research method and conclusions achieved in this part can provide a reference for the rapid realization of the pyroshock test condition.