Molecular Dynamics Simulation On The Mechanics Performance Of Negative Poisson’s Ratio Metallic Nanowires

Negative Poisson’s ratio materials are widely used in modern production activities due to their excellent properties.In this paper,the molecular dynamics simulation method is systematically presented and used to conduct an in-depth study of eccentric cubic metal nanowires.The aim of the study is to investigate the deformation mechanism of this metallic material under axial loading,as well as to analyze the effect of different factor variations on its mechanical properties and Poisson’s ratio behavior.In this paper,a basic model of five face-centered cubic metal(Cu,Ag,Au,Ni,Al)nanowires with square cross-section was constructed using LAMMPS(Large-scale Atomic/Molecular Massively Parallel Simulator)with the model size set to 6a×6a×300a,where a is the lattice constant of each metal.In addition,three different crystallographic orientations were modeled for each metal nanowire by converting the cell orientation,and the nanowire axes corresponded to the[100],[110],and[111]crystallographic orientations,for a total of fifteen models.(1)The deformation mechanism of the models during axial loading was analyzed by compressing and stretching them axially at a temperature of 300 K at room temperature and rate,respectively,and the asymmetry of their mechanical properties and Poisson’s ratio behaviors were discussed in detail in conjunction with the changes of the microstructure inside the crystal,and the negative Poisson’s ratio behaviors of the nanowires were discussed.The distribution of orientation factors is approximately the same for the five metallic materials under the same crystallographic orientation and loading conditions,while the ratio of yield strength is slightly different,and this difference is most obvious down the[110]crystal.The Poisson’s ratio destabilization bifurcation occurs in both tensile and compressive loading modes,and the negative Poisson’s ratio after bifurcation mainly appears in[110]crystal direction.(2)The model was subsequently simulated by setting different temperatures(0.1K-400K)to explore the relationship between Poisson’s ratio and temperature.As the temperature increases,the Poisson’s ratio in the elastic phase of nanowire[100]increases a little,and the bifurcation distortion of Poisson’s ratio in[100]and[111]crystalline directions will be advanced,but no negative Poisson’s ratio phenomenon will occur in the temperature change range;the minimum Poisson’s ratio of nanowire[110]shows negative values in the temperature range,and there is a critical transition temperature for the minimum Poisson’s ratio.(3)The model is then set to different loading rates(5×10~8/s,4×10~8/s,3×10~8/s,2×10~8/s,1×10~8/s,5×10~7/s).With the increase of strain rate,the bifurcation distortion of Poisson’s ratio is slightly delayed when[100]crystalline axial loading to and does not produce extreme Poisson’s ratio phenomenon in the 0.5 5×10~8/s loading rate range;[111]crystalline nanowires show negative Poisson’s ratio behavior briefly at a specific loading rate;and the minimum negative Poisson’s ratio of[110]crystalline nanowires satisfies a certain linear relationship with the strain rate.The results of this paper provide a theoretical reference to further explore the negative Poisson’s ratio behavior of face-centered cubic metals under axial loading.