The Study On Mechanical Properties Of 3D Structures With Negative Compressibility

With the rapid development of modern science and technology,higher requirements for materials properties are needed.Some of the properties are rarely found in nature materials,so the research and design of new materials with special properties have already become one of the key issues for the academe and the field of engineering.During the improvement of the mechanical properties,the broad application prospects of a series of materials with special properties are viewed and the material with negative compressibility is included.Common materials will contract in every direction when they are compressed,however some materials with negative compressibility will expand in one or more directions when subjected to the hydrostatic pressure.Now there are some limitations in the study of negative compressibility,for example,the structures which is used for achieving negative compressibility are almost two dimensional and although the 2D models are simpler to analyze,somtimes the simplification from 3D models to planar structures may lead to differences between conclusions and actual results.And the 3D models with negative compressibility are very rare and the structures of them are all excessively complex.So the design as well as the study of 3D structures with negative compressibility is becoming more significant.In view of this,we use the 2D wine-rack structure to design the 3D models and two three-dimensional models have been designed.The theoretical equations for the mechanical properties of these two models were derived and the effect of geometry on the property of negative compressibility was discussed.By comparison,the hinging octahedron model is more useful when used to achieve negative compressibility so the further study including simulation analyses and experiment exploration of this model were carried out.And detail work of this paper is as follows:1.Based on the 2D wine-rack structure,two 3D models were designed(i.e.the hexahedron models and the octathedron models).According to the basic theory of mechanics and the energy approach,the expressions of the Young's moduli,Poisson's ratios and compressibility properties are derived.The effect of negative compreesibility was also analyzed based on these expressions.Finally,the hinging octathedron models which can achieve larger negative compressibility were choosed for the further study.2.The finite element models of the octathedron models were established based on the analysis soft ANSYS.The mechanical properties of octathedron model including Young's moduli and Poisson's ratios are analyzed by simulation.And the expressions of linear compressibilitis in OX1,OX2 and OX3 directions are also derived.By comparison,the validity of the finite element models and the correctness of theoretical results were verified.3.The samples of hinging octathedron models were made through 3D printing and the mechanical properties of these models were measured experimentally.By comparison,we found that the results of experiment accord with the ANSYS results and the thereticals results so the validity of the finite element models and the correctness of theoretical results were verified.