Structural Dynamic Analysis Of Spacecraft Based On Impulse Based Substructuring Method

In modern aerospace industry,the dynamic response characteristic of spacecraft structures is a crucial criterion for spacecraft structure optimization and the structural safety of spacecraft,because it is an essential representation of the dynamic environmental conditions.The modern aerospace industry requires high performance,low redundancy and high reliability,which makes the analysis necessary for multiple load cases and missions under practical environment conditions.As an effective tool,the physical simulation is highcost and is difficult to simulate the real environment conditions,so it cannot satisfy the requirements for multi-mission analysis.Benefitting from the improvement of computational ability,numerical simulation has been the main method of dynamic analysis for spacecraft structures.However,with the continuously increasing complexity of spacecraft structures,the numerical computation cost boosts and the existing finite element method encounters difficulties in analysis for multi-mission and multiple environmental conditions.Based on the characteristics of parachute ejection and parachute opening during entry,descent and landing(EDL)of Mars lander,this paper uses the finite element substructure and impulse based substructuring synthesis reduction method to conduct the dynamic analysis for multiple environment conditions.Meanwhile,by the secondary development of ABAQUS software,this paper proposes an entire analysis process for the finite element substructure and impulse based substructuring synthesis reduction method.Particularly:(1)The development history and state-of-art of the time-domain substructure method,the dynamic analysis for complex spacecraft and numerical simulation based on the secondary development of ABAQUS software are summarized.(2)The basic theory of the impulse based substructuring method is introduced.Based on the Duhamel’s integral for the single-degree-of-freedom system,the impulse response function matrix,interface compatibility condition and the motion synthesis equation are deduced for multi-degree-of-freedom system.Furthermore,the numerical realization method of impulse input is discussed and the numerical scheme of the impulse based substructuring and the finite element substructure synthesis method is detailed.Finally,the entire analysis process of synthesis reduction method is summarized.(3)Based on the EDL process of Mars lander,the finite element model of Mars lander for dynamic analysis is developed.According to the multiple load cases corresponding to the variable loads on the back shell during the parachute ejection and opening,the impulse based substructuring and the finite element substructure synthesis model is established,which preserves the high accuracy but improves the computational efficiency drastically compared with the full-order finite element model.Finally,this model is compared with the full-order finite element model,which verifies its effectiveness.(4)Based on the reduced model,the dynamic analysis of the parachute ejection and opening states is conducted,where the parachute ejection and opening loads are reasonably simplified and applied to the finite element model.The influences of three load cases,i.e.the peak duration of parachute ejection loads,the suspension points number of parachute and material stiffness,on the dynamic responses are analyzed.These analysis results are helpful to design the structure and EDL project.(5)Because the integrated finite element substructure and impulse based substructuring reduction model for dynamic response analysis is complex to be applied,this model is integrated into the ABAQUS platform by the secondary development of ABAQUS,which improves the modelling efficiency.Finally,a numerical example is used to verify its effectiveness and efficiency.