Molecular Dynamics Simulation Of Single Crystal Nano Copper With Voids

In the current engineering materials science,the defect destruction of metal materials is a non-negligible failure mode.By studying the defects of the microscopic nano-metal system,the mechanical properties of the metal nano-materials can be improved,and a new process method for manufacturing high-performance metal materials can be provided.In this dissertation,the molecular dynamics simulations of single-crystal nanocrystalline copper containing voids were carried out by using the molecular dynamics method and EAM potential function.The mechanical properties of single-crystal nanocrystalline copper containing voids were studied.The mechanical behavior of copper nanosheets with voids under biaxial loading was studied.The effects of void position,void radius and void shape in the model on the mechanical properties of copper nanosheets are discussed.The main cause of fracture is the correspondence between shear stress and dislocation.The dislocations are formed at the corners of the nano-square sheet.As the deformation increases,the dislocations approach the center of the void.The radius of the void affects the destruction time of the nanosheet.The larger the void radius,the smaller the shear stress and the earlier the model is destroyed.The void location affects the distribution of dislocations.The closer the void is to the boundary,the greater the shear stress of the model.Under symmetrical loading conditions,the symmetric position voids exhibit different mechanical properties.When the void is non-circular,the new asymmetric dislocation line will appear at the tip,resulting in different mechanical properties.The mechanical properties of copper nanocubes with different sizes cubic voids under triaxial tension are studied.In addition to the void size,the effects of different crystal orientations are also taken into account.In the study of [100] nanocubes,the concepts of hydrostatic stress,true stress and logarithmic strain are introduced.Through analysis,hydrostatic stress replaces the triaxial stress of the model.True stress is slightly greater than traditional nominal stress.As the ratio of voids increases,the yield strength decreases.In addition,the mechanical properties of [110] and [111]-oriented copper nanocubes with voids are investigated from the perspectives of energy,stress and deformation.The difference of crystal orientation can lead to differences of triaxial stress.No matter which direction of stress,with the size of void larger,it becomes smaller.For these two kinds of crystalline copper nanocubes,the larger the void size,the easier and more regular the destruction of the model.The single crystal copper ellipsoid nanospheres under external normal tensile load are studied.Normal stress and Mises stress are introduced to describe the mechanical properties of the material.Through the simulation of uniform thickness nanoshells,variable thickness nanoshells and variable radius nanoshells,the effect of thickness on the yield behavior and other mechanical properties is clarified.The potential energy,stress and deformation of the nanoshells are studied.The dislocation lines of the nanosphere profile will form an octagon or that add a quadrilateral.Variable thickness nanoshells slightly disrupt this shape.The potential energy of nanoshells will increase after a stable phase.The thickness of the nanoshell has a certain influence on the elastic phase,and nanoshells of different thickness have different mechanical properties.The dislocation patterns of the nanoshells with the same thickness and different radius ratios are extruded octagons.The external shape of the nanoshell affects the loading direction and influences the trend of the curve.The nano sphere structure is more stable than the ellipsoidal structure.The influence of different velocity on the nanoshell is studied.It is found that the potential energy and Mises stress at the high rate of tensile rate are the largest.