Structural Design Of Mechanical Cloak Based On Pentamode Metamaterials

Stealth technology is widely used in military applications.It is mainly divided into electromagnetic,acoustic,thermal and mechanical stealth cloaks.With the successful application of coordinate transformation method in electromagnetic stealth cloak,acoustic stealth cloak and thermal stealth cloak based on coordinate transformation principle appear one after another.For mechanical stealth,the basic condition based on coordinate transformation stealth theory cannot be satisfied,that is,the form of control equation is not always consistent when coordinate transformation occurs,so mechanical stealth based on core-shell model Be put forward.In this paper,the structural design of mechanical stealth cloak is carried out by using this method.In this thesis,the coordinate transformation theory and the core-shell model equivalent transformation theory are introduced,and the core-shell model theory is selected as the theoretical basis of mechanical stealth.According to the requirement of equivalent transformation theory of core-shell model,five-mode supermaterial is selected as the material foundation of cloak structure.The formulas for calculating the equivalent shear modulus and volume modulus of five-mode supermaterial are given.In this thesis,the static analysis of the elastic properties of pentamode metamaterials is carried out.The effects of structural parameters,matrix properties and material cross-section shape on the equivalent shear modulus,the equivalent bulk modulus and the ratio of the two equivalent moduli of five-mode supermaterials were analyzed respectively.The data curve was fitted by MATLAB.In addition,based on the simulation and fitting results,the approximate formulas of the equivalent bulk modulus and shear modulus of the five-mode supermaterial are given.Based on the core-shell equivalent transformation theory and the analysis conclusion of the elastic properties of five-mode supermaterial,the structural parameters of five-mode supermaterial and the structural model of cylindrical cloak are determined,and the stealth performance index is proposed,the stealth performance is analyzed,and two kinds of non-cylindrical cloak structures,cuboid and cube,are explored.Comparing the two processing methods,the traditional 3D printing technology is selected as the processing method.Because the cylindrical cloak has better stealth performance,the designed cylindrical cloak was processed and manufactured.