Active Regulation Of Negative Possion's Ratio Of Mechanical Metamaterials

Poisson's ratio provides a basic index to measure the performance of materials under elastic strain.At present,the research of negative Poisson's ratio structure is mainly to obtain the negative Poisson's ratio effect by designing the geometric shape or structure of materials.People's research direction has gradually shifted from the design of negative Poisson's ratio structure to the adjustable research of structure's Poisson's ratio in recent years.Through the parametric design of structure,the required mechanical properties and deformation form can be shown.In this paper,a kind of two-dimensional circular porous negative Poisson's ratio structure is designed,and its internal structure is improved.The solid structure in the original unit is changed to a structure filled with small round pieces.The deformation process of the structure was studied by ABAQUS simulation.By changing the filling condition of the small disk in the basic unit of the structure,the unit itself presents positive Poisson's ratio or negative Poisson's ratio effect.Then by changing the combination ratio and arrangement mode of positive and negative Poisson's ratio units,the whole structure of multiple units can adjust the Poisson's ratio from negative to positive.Further analysis of the vibration characteristics of the two-dimensional structure shows that when the structure is filled and not filled,the vibration shapes and modes vary greatly,it can be found that,when the structure is filled or not,its vibration form and mode are quite different,that is,whether the structure is filled or not can not only adjust the mechanical properties of the structure,but also its physical properties.The modal of the structure is obtained by free vibration experiment.Change the arrangement of structural units to study the propagation law of vibration in the structure;The strain energy absorbed during the rotation of structural units with different filling ratios was studied by changing the filling ratio of structural units.In addition to the filling of small cylinders to adjust the Poisson's ratio within the structural unit,the Poisson's ratio can also be adjusted by shape memory materials or by using microstructures to change the stiffness within the unit,such as cross flower structure and axle structure.The stiffness and Poisson's ratio of the structure can be changed by using different filled microstructures.According to the above two-dimensional structure,a one-dimensional cylinder structure and two three-dimensional structures are further designed,and the compression process is simulated and analyzed.