Mechanical Properties Of Single Crystal Copper Nano Typical Components By Molecular Dynamics

With the wide application of nanoscale devices,the mechanical properties of nano-scale components have been paid more and more attention.However,the experiments of nano-level components are generally not easy to be realized,and due to the enhancement of computing power,numerical simulation techniques are widely used in the calculation of nanometer components.Molecular dynamics is one of the most widely used methods.In the paper mechanical properties of several single crystal copper nano components are simulated by molecular dynamics.In order to analyze the deformation of nano components,the software for displaying the data is developed.The software is based on C# program development.It introduces the OpenGL display package and calls the DLL external dynamic link library written by C++.3D transform algorithm is proposed to realize the transformation process of the component,which facilitates the visualization of the model.The mechanical properties of different orientation copper nanocubes are studied.In order to study the difference of orientations,the orientation size is given,which is a good measure of the difference between the orientations.When the orientation sizes are close,the properties at the directions are similar.The different properties of nanocubes are analyzed from three aspects: energy,stress and deformation.Because of the same temperature,the value of the kinetic energy is constant.And the value of the potential energy has a lot to do with the orientation.The larger the orientation size,the greater the absolute value of potential energy and the smaller the change of potential energy.The stress of three orientation nanocubes at three directions are analyzed.The closer the orientation size,the more similar the stress curve.After that,the average stress and Mises stress curves of the three models are discussed,where the Mises stress curve is found within the average stress curve,and the stress values of the Mises stress curve are more secure.The three models have different deformations.The deformation of [100] nanocube starts at the corner,[110] nanocube starts from the edge,and [111] nanocube breaks from the surface at first.Based on the theory of molecular dynamics,nature strain based on atomic motion is proposed,and dynamic Poisson's ratio and dynamic Young's modulus based on nature strain are defined.The dynamic Poisson's ratio and dynamic Young's modulus of the copper nanorods with different orientations and section sizes under tensile loadings are analyzed.There is a correspondence between the nature strain and the stress when stretching,and the nature strain reflects more mechanical properties.The dynamic Poisson's ratio at the two directions of the cross section is directly related to the orientation,and the difference between the orintation sizes determines the difference of dynamic Poisson's ratio.The dynamic Young's modulus is related to the orientation size at the stretching direction.The larger the orientation size is,the smaller the slope of the stress curve is before yielding,and the more stable it is.The larger the section area is,the smaller the dynamic Poisson's ratio is,and the flatter the curve is,but the stable value of Young's modulus is the same.After that,the copper nanorods with different orientaions and different lengths are simulated under compression.The deformation of compression is a process of accumulation and transmission,which is different from tension,so the properties are different.There is jumps in dynamic Poisson's ratio and dynamic Young's modulus during nanorods compression,and the timing of jump is related to the orientation and length.Compressed copper nanorods are sensitive to length and there are stability issues.Based on the nature strain of rectangular coordinate system,the nature strain and corresponding nature strain ratio of cylindrical coordinate system are defined.The tensile behavior of hollow copper nanocylinder is simulated.The influence of different thicknesses and different tensile rates on the mechanical properties of nanocylinder is considered.It is found that the wall thickness of hollow nanocylinder directly influences the properties of the nanocylinder.When the hole size reaches a certain value,that is,when the wall thickness is very thin,values of the potential energy of the nanocylinder during the relaxation change greatly,the section shape of the model will change greatly,which leads the different properties of thin-walled nanotubes.The relationship between average stress and Mises stress is analyzed and fitted.The tensile rate mainly affects the change of nature strain rate of the hollow copper nano-cylinder,resulting the difference of conventional strain at the time of fracture.