Research On Theoretical Models And Optimition Design For Energy Absorbers Of Legged-type Lander

Disposable energy absorber for legged-type lander has high reliability, simple structure, lightweight, small volume, strong adapting ability to the working environment, and no secondary damage to the protected objects, etc. So it is widely used in the field of planetary detection. Along with the startup of Chinese lunar exploration project, developing the study on the characters and related key techniques of disposable energy absorber for legged-type lander to guide the energy absorber design has significant technology and political significance.To instruct the follow-up research on the energy absorption characteristics of legged landing energy absorber and its related theories, the related basic theory research of the energy absorber used in legged-type lander is carried out, which includes the structure principle of the legged-type lander, and its energy absorber including various energy absorber and their characteristics. The evaluation methods of the energy absoption performance are put forward for the systematic comparison of energy absorption characteristics of the various energy absorbers, to provide a theoretical guidance for the energy absorber design.Taking the hexagonal metal honeycombs, which have double thickness vertical walls (non-uniform commercial metal honeycombs), as the research objective. Basing on its symmetry structure, the paper studies Y-shaped honeycomb cell. According to law of energy conservation, this study adopts Mises yield criterion and Tresca yield criterion to establish the constitutive equation of the static plastic collapse stress under out-of-plane compression and the theoretical model of the length of plastic hinge respectively. Establish the theoretical model of metal honeycomb material's elastic collapse stress. Respectively using the plastic hinge length calculation model in this paper and given calculation equation in existing literatures to establish the theoretical model of metal cellular material's limiting strain. Through the experiments on eighteen kinds of different specifications of the aluminum honeycomb specimens, the validity of theoretical models of plastic collapse stress under the out-of-plane compression, elastic collapse stress and the limiting strain theory is verified. It settles the foundation for the follow-up out-of-plane compression characteristics research of metal honeycomb that under the different temperature and strain ratio, and design of energy absorber for legged-type lander.Establish the plastic collapse stress theoretical calculation model of metal honeycomb under impact loading. Through the compression experiments of twelve kinds of different specification aluminum honeycomb specimens under impact loading, the correctness of theoretical model is verified. Set up the plastic collapse stress'theoretical calculation model of the metal honeycomb material under different environment temperatures and different strain rate. And the experiment verified the correctness of the established theoretical calculation models. Through analysis of the cushion mechanism and cushion characteristics of metal honeycombs, this study puts forward the ways of improving metal honeycomb's absorber performance, which provides a theoretical basis of such energy absorber design. Taking the minimal mass and minimal volume as the final objection, and taking the design requirement and safe operation as the boundary conditions, the optimization design method for legged-type lander that made of metal honeycomb energy absorber is provided. The parameter programming for optimization is made to improve the design efficiency.Establish the plastic collapse stress theoretical model of metal foam under impact loading. Through compression characteristics experiment of 8 kinds of aluminum foam specimen with different relative density under impact loading, the correctness of the established theoretical calculations model is verified. Establish the plastic collapse stress theoretical model of the metal honeycomb under different temperature and with different strain rate environment. Experiment proves the correctness of the established theoretical calculation model. Taking the minimal mass and minimal volume as the final objection, and taking the design requirement and safe operation as the boundary conditions, the optimization design method for legged-type lander that made of metal foam energy absorber is provided. The parameter programming for optimization is made to improve the design efficiency.Set up thin-walled tube plastic energy absorber's theoretical model under impact load and different temperature environments. Derive the deformation capacity of the thin-walled tube plastic energy absorber, as well as the requirements on safety and reliability assurance of absorber. These provide the theoretical basis on thin-walled tube plastic energy absorber. Analyze the deformation mechanism of the absorber and put forward the improve ways on absorption characteristic of thin-walled tube plastic energy absorber. Do experiment study on e absorber characteristic of the thin-walled tube plastic energy absorber filled with both metal honeycomb and metal foam. Taking the minimal mass and minimal volume as the final objection, and taking the design requirement and safe operation as the boundary conditions, the optimization design method for legged-type lander that made of thin-walled tube plastic energy absorber is provided. The parameter programming for optimization is made to improve the design efficiency.Analyze the plastic collapse stress theoretical calculation model's relationship between metal cellular materials and metal foam, based on this relationship, a unified theory of plastic collapse stress calculation model about relative density between honeycomb and metal foam is set up. It provides the theoretical basis for follow-up cushioning property comparison of metal honeycomb and foam. Systematically compare the legged-type lander's energy absorption characteristic between metal honeycomb energy absorber, metal foam energy absorber and thin-walled metal tube plastic energy absorber. And this provides the theoretical basis and technical guidance on legged-type lander absorption plan.