Molecular Dynamics Simulations Of Single Crystal Copper Component Mechanical Properties With The Holes

The computer simulation technology for analyzing the material micro mechanical properties is developed to atomic and molecular level. Explaining macro properties by micro study helps to solve practical engineering problems deeper, which is of great significance in practice.Focusing on related theory of applied molecular dynamics, through building the model with Fortran programming, simulations of tensile, bending, shear process of single crystal copper beams with no defects and with holes are conducted respectively, the effect of defects in nanometer scale on the mechanical behavior of single crystal copper beams is researched in this paper.By comparing the potential function of embedded atom, the mathematical expressions of interaction between atoms are deduced. And on the basis of it, the graphs of potential function and the interactions between two atoms of single crystal copper material are drawn. According to the theory of molecular dynamics, using Verlet-velocity algorithm, using temperature controlling method of direct speed calibration, because the Fortran language is more suitable for scientific computing, and using Fortran programming, a two-dimensional model is established and the subsequent calculations are also analyzed. Because of the programming, the correctness and feasibility of program are needed to be verified. When the relaxation starting, the atoms in the model influenced by interatomic forces began to move freely, after a certain numbers of relaxation, kinetic energy, potential energy and the average strain of the system approaches equilibrium, which is consistent with the data of the model calculated by using VC++ programming, and verifies the correctness and feasibility of programming. When relaxation is completed, fixing one end of the model, applying certain loads, changes of the parameters and the final model in the process of the tensile, bending, shear are researched.Through the effect of external loads, the interatomic forces, the relative position between the atomic, and the configuration diagram of the model changes in full relaxation stage. Because of the speed calibration, the energy of power system increases, which mainly lies in the increase of potential energy of the system. The energy of power system doesn’t increase until the destruction occurs, during which the atomic bonds rupture, a lot of energy lose, and the total potential energy of the model system reduce. After recording the data, the average strain curve and deflection curve during bending are drawn, from which it is concluded that the tensile failure process is close to the influence of size effect and surface effect on brittle material under the macroscopic process. While sliding and dislocation effect makes mechanical properties of single crystal copper beam in nanometer level not the same under the macroscopic process, the existence of defects makes elastic modulus, failure stress of the material reduce significantly.In the process of bending, the existence of defects has a good effect on bending in a certain extent. Beside, the interatomic forces in lower and upper level have a great influence on shear process in a micro condition.