Time-Domain Substructuring Methods And Application In Landing Dynamics Of Lunar Lander

During landing process,the lunar lander will suffer a short-time impact.To assure the safety of the lunar lander and its payloads during the impact,the landing dynamics should be analyzed.Based on the landing dynamics,the dynamic environment for the concerned areas of the lunar lander should be predicted.The finite element(FE)model with high accuracy can be developed to effectively fulfill these targets.However,due to the huge size of the finite element model and the expensive computing cost,the original finite element model cannot meet the requirements for the rapid design in engineering.Therefore,it is necessary to introduce an accurate and efficient method for the calculation of structural dynamic responses.The time-domain substructuring methods are efficient tools to conduct dynamic analysis for complex structures.However,for complex structures such as a lunar lander,the dynamics of different components are significantly different and the connections between adjacent components are highly various and complex,so the existing time-domain substructuring methods are difficult to be applied.Enlighted by these problems,this thesis considers the synthesis of multiple time-domain substructures with various interface connections and proposed some innovated solutions.Moreover,the proposed methods are applied to the landing dynamic analysis of a lunar lander.The main contents of this thesis are arranged as:(1)The time-domain substructuring methods and the substructuring interface techniques are summarized.Based on the summarization of landing dynamic researches of the lunar lander at home and abroad,the necessity to introduce the time-domain substructuring methods for the landing dynamics is emphasized.The basis theories of impulse based substructuring(IBS)method are detailed.Those contents supply a primary support for the further research on the improvement and extension of the IBS method.(2)A novel method to accomplish the synthesis of IRFs of substructures with non-matching interfaces is developed.By considering both the force balance and the energy conservation condition on the interfaces,the criterion for constructing interpolation shape function is proposed.Based on this criterion,two meshless shape functions,namely moving Kriging and moving least squares shape function,are adopted to solve the non-matching interfaces problem.Finally,numerical examples are introduced to investigate performances of the proposed method.(3)Considering the different descriptions of substructures and the various interface assumptions,a method for assembling multi-domain substructures with general joints is proposed.In this proposed method,the rigid joint,the elastic joint whose connecting force can be expressed in explicit form and the combination of rigid and elastic joints are regarded as general joints.By fusing all dynamic information of substructures into the motion equations of the general joints,the proposed frame realizes the synthesis of IBS substructures,FE substructures and modal substructures.The effectiveness of this proposed method is validated by numerical examples.(4)The proposed time-domain substructuring methods are applied to landing dynamic response analysis of a lunar lander.The solved problems include: the synthesis of the IRFs of the central body and rover with non-matching interfaces;the dynamic response analysis of the central body(IBS substructure)and solar wings(FE or modal substructures)assembled by linear or nonlinear joints.The results demonstrate the effectiveness and efficiency of the proposed method,which provides a new idea for studying the dynamics of complex structures such as the lunar lander and supplies a foundation for structural optimal design considering the dynamic properties during landing.(5)Based on the proposed time-domain substructuring method,the dynamic model of lander is developed to conduct the structural optimal design of solar wings.By introducing this substructuring method,the landing dynamic environment of lunar lander can be considered in the optimal design.Through the optimization analysis,the proper structural parameters are obtained and the dynamic environment of concerned areas on solar wings during landing is ameliorated.These results pronounce that the proposed time-domain substructuring method can be effectively applied to the structural optimal design of complex structures and remarkably improve the efficiency of structural optimization,and the dynamic analysis can provide guidance for the structural design of the lunar lander.