Structure And Performance Analysis Of New Spatial Large Negative Poisson’s Ratio Based On Crystal-mimic Theory

Negative Poisson’s ratio structure has excellent performance,which is widely used in aerospace,military and building fields.However,the existing structure remains deficient.On the one hand,these structures cannot show a unified large negative Poisson’s ratio effect in three directions.On the other hand,the initial stress value of most structures is far greater than the platform stress value when subjected to medium-low velocity impact.The energy absorption efficiency of structures is low.Therefore,it is necessary to design a new spatial large negative Poisson’s ratio structure.In this paper,two kinds of spatial large negative Poisson’s ratio structures were constructed by using the method of crystal-mimic.Structures are constructed by elastic curved beams instead of bonds between atoms.The negative Poisson’s ratio effect of two structures was verified by simulation and experiment.Then the vibration reduction performance and energy absorption performance of the two structures were analyzed.The negative Poisson’s ratio structure was placed in the sole,and the sole with a spatial large negative Poisson’s ratio structure was designed.The energy absorption and vibration reduction performance of the shoe sole with negative Poisson’s ratio structure was obtained by finite element simulation.The main research contents are as follows :(1)Two kinds of structures with spatial large negative Poisson’s ratio were constructed by using the method of crystal-mimic.The first structure is wave-like structure and the second is symmetrical structure.Negative Poisson’s ratio effect in three directions was studied by finite element analysis,and two structural Poisson’s ratio value was calculated.Tensile and compressive experiments were carried out in the x,y,and z directions,respectively.The structure characteristics of the three-direction large negative Poisson’s ratio were well verified.The shape of the curved beam has a great influence on the Poisson’s ratio of the structure.The negative Poisson’s ratio value of the two structures decreases nonlinearly with the increase of the coordinates of the intermediate control points.(2)Taking the vibration level difference as an index,sinusoidal excitation load was applied to the two structures in the x,y,and z directions,respectively.The vibration reduction performance of the structure was analyzed by finite element simulation.Comparing the vibration level difference values in three directions,it is found that wave-like structure has the same vibration reduction performance in three directions,and symmetrical structure also has the same vibration reduction performance in three directions.The vibration reduction performance of symmetrical structure is higher than that of wave-like structure.(3)Taking specific energy absorption and crash load efficiency as indexes,the dynamic impact simulation of two structures in x,y,and z directions were carried out,respectively.The results show that wave-like structure has the same energy absorption performance in three directions,and symmetrical structure also has the same energy absorption performance in three directions.Symmetrical structure absorbs more energy when subjected to shock compression.Symmetrical structure shows higher energy absorption efficiency,better stability,and better performance.(4)The energy absorption and vibration reduction performance of the shoe sole was analyzed and compared with shoe sole without negative Poisson’s ratio structure.The results show that the sole has higher energy absorption and vibration reduction performance than the sole without negative Poisson’s ratio structure,which can reduce the impact of the ground on the feet and play a good protective effect on human body.