Effect Of Crystal Defect On Strength Of Single Crystal Copper

In the research on molecular dynamics about the metal material, people found thatthe actual metal crystal structure differs from the ideal metal crystal structure, ideal metalcrystal structure of atomic lattice is completely in accordance with the rule arrangement,while the actual metal crystal structure in the different level land is existing defects incrystals, the crystal defects have some influences on the metal material mechanicsperformance.So using molecular dynamics method to research this influence has valuablesignificance.In thie article,we using molecular dynamics method simulated and researched themetal material mechanics performance with defects. First, we introduced applyingperiodic boundary condition method in detail, builted the copper material model withperiodic condition, calculated the size of7a×7a×30a model, and then obtained variationsof systemic kinetic energy and atoms coordinate during the free relaxation process, studidthe result with theory, determined the free relaxation time step. When model are droved toa equilibrium position, we applied external load to the model, the force vaule from zeroincrease gradually to simulate the static loading process.When the copper material undertensile stress fracture damage, we obtained the stress-strain relation curve and atomicdistribution maps. We compared copper bar and copper material's result, their similaritiesand differences are analyzed in detail. Second, we added the same holes in copper bar andcopper material, the holes' radius is increased from0.2a to0.35a. The two groups ofmodel is applied by external loading until fracture. In the simulation process, we obtainthe stress-strain relation curve and holes' radius-strength relation curve; Final, the copperbar model has been builted with screw dislocation, calculated the model and determinedthe free relaxation time step. When model are droved to a equilibrium position, we appliedexternal load to the model, the force vaule from zero increase gradually to simulate thestatic loading process.When the copper material under tensile stress fracture damage, weobtained the atomic distribution maps, stress-strain relation curve and modulus ofelasticity curve.