Simulation Of Tension And Shear Of Nano Single-crystal Copper Based On Molecular Dynamics

The deformation process of uniaxial tension and shear which EAM potential constructed by Doyama within (111) is Simulated in the thesis and ploted the curves both uniaxial tensile deformation and shear deformation based on the caculated data.The results of uniaxial tensile deformation show; the tension process of nano crystal copper consists of an elastic period and a plastic period. When deformation is elastic the structure of initial atomic system changes little, while in plastic period change is obvious. in the phase of plastic deformation, the crack appeared in inner construction ,and with it broaden, the hole formed, and finally snapped. The transformation occurred in plastic phase including break of metal bond, movement of atoms and pores, migration of grain boundary.The results of shear deformation show; when deformation is elastic the initial configuration of atomic system changes little, obvious change is observed in plastic period, such as break of metal bond, movement of atoms and pores, migration of grain boundary. With the shear deformation broadened, the movement and reconbine of vacancy prick up, the system's energy begin increase again. The shape of the boundry change further, and cause new metal bond break.The analysis of strain-stress curves show; the deformation mechanism directly determines the corresponding stress-strain curve; the curve is linear in elastic period which coincides with the Huke Law; the curve fluctuates greatly in plastic period according to the microscopic deformation mechanism. The break of metal bond cause a sudden drop of the curve, however, the movement of atoms and pores can reduce the energy of whole system temporarily, which makes a new ascendent to the stress-strain.The relationship between strain and stress is related to macro continuum as well as the construction of inner atoms and the microcosmic transformation mechanism ,it should be the better direction to study the relationship of strain and stress from the beginning of microcosmic and the combination of Microcosmic and macrocosmic.