Negative Compressibility Of 3D Cellular Models Constructed By Hinging Hexagonal Truss Mechanism

Negative compressibility is a special material characteristic of late discovery and research in supermaterials.Generally speaking,when the materials are under hydrostatic pressure,they should contract in all directions,but researchs have shown that materials with negative compressibility show an uncommon behavior under uniform pressure,which can increase in dimension along one or more directions.Although many different structures have been proposed and analyzed,there are still many limitations in the development of negative compressibility materials,such as most negative compressibility structures that are studied in two dimensional planes,such as wine-rack-type.Also the simplification of the 3D model into a 2D plane structure causes the deviation between the experimental results and the theoretical models.Therefore only few studies extending negative compressibility to 3D space and only few methods to build a 3D structure with negative compressibility have been proposed.The existing 3D structure is not only small,but also complex.Therefore,the research on the structure of three-dimensional negative compressibility is still meaningful in the research significance and development space.In this study,we use the hinging hexagonal truss mechanism to construct 3D models and three different structures are proposed through a same method.And the expressions of the mechanical properties including on-axis Young’s moduli,Poisson’s ratios and compressibility properties are derived and discussed.Through the comparison and analysis of these three models,this paper explores the factors that affect the negative compressibility of the structures,and makes further finite element simulation and experimental verification of the models.The specific research content is composed of the following three parts:1.We discuss three models based on the design of hinged hexagonal truss mechanism,and these three models are constructed by the orthogonal arrangement of the hinging hexagonal truss mechanism.The negative compression mathematical expression of three models is deduced by traditional mechanical method and energy method.By using matlab software to draw the compressibility diagram of the three models,the paper analyzes and compares the results,and finds that the h/l andθcan greatly influence the negative compressibility of the model.And it is found that the ModelⅡhas greater negative compressibility in the three models designed by the same modeling idea.The arrangement of the framework and the layout orientations of 2D mechanisms can also have a great influence on the negative compressibility effect.2.The ModelⅡis further analyzed and verified.Through the ANSYS software Workbench module,the model analysis of 15 finite element models of ModelⅡis analyzed,the three deformation values of the model in three directions are obtained,and the Young’s moduli and Poisson’s ratios are calculated,and the compressibility results of the model are deduced.Using MATLAB software to draw the graph of its theory and simulation results,the finite element model is found to be the correctness of the theoretical model,but the error is small and the trend is consistent.3.The experimental results of the three displacement were obtained by means of mechanical method,the results of the line compressibility result are derived from the calculated Young’s moduli and Poisson’s ratios.And by comparing with the simulation results,we can see that although experimental results exist error,the error is small and the curve trend is the same,and it can be verified that it is consistent with the conclusion of the simulation calculation and the theoretical derivation,and ModelⅡdoes have negative compressibility.