The Research Of Tensile Deformation Mechanism Of Nanocrystalline Copper Based On Molecular Dynamics Simulation

In this paper, the tensile deformation process of the single crystalline copper nano rodand bulk were simulated respectively based on the parallel molecular dynamicssimulation technique. The surface effect on single crystalline copper nano rod werestudied. Polycrystalline nano bulk were constructed via VC++program which based onVoronoi method. The effect of microstructures such as grain boundaries on the tensiledeformation mechanism were explored. The effect of the cross section shape on thetensile deformation mechanism were analyzed by investigated the tensile deformationprocess of polycrystalline nano rod with square cross section and circular cross section.The research in the issue is of great theoretical value on the comprehensiveunderstanding of the mechanical property and deformation mechanism on NEMSconpotent.The computing platform of large scale parallel simulation were built based onLAMMPS software. The atomic motion images were acquired by simulate the tensiledeformation process of single crystalline copper nano rod and bulk. The role of freesurface in the tensile deformation process of single crystalline copper nano rod wereanalyzed and revealed. The results indicate that defects atoms emerged in the place withhigh atom energy, and yield strength of single crystalline copper nano rod was smallerthan that of the bulk under the effect of surface effect. The single crystalline coppernano rod and bulk with different deformation mechanism.Secondly, polycrystalline nano bulk were constructed via VC++program whichbased on Voronoi method, and the microstructure were analyzed. A higher percentage ofgrain boundary atoms were acquired. The energy distribution of cross section is basinshape, it imply that the atom energy of grain boundary atoms higher than that of thegrain atoms. The tensile deformation process of polycrystalline nano bukl weresimulatied and the result indicted that the grain boundary play an important role. Theyield strength is smaller than that of the single crystalline bulk for the defect atomsemerge easier near the grain boundary which with high energy. On the other hand, thegrain boundary resistant the the expansion of the dislocation, it is the reason of thephenomenon strain strengthening. The trend of rotation were acquired and it imply thatthe deformation mechanism was dominate by the grain boundary sliding and grainrotation.Finally, polycrystalline nano rod with square cross section and circular cross sectionwere constructed via VC++program which based on Voronoi method. The atomicmotion images were acquired. The result indicted that the cross section shape couldaffect the atom energy distribution of polycrystalline nano rod surface atoms. The percentage of the surface atoms of square cross section polycrystalline nano rod is lower,and it is the reason that the yield strength of square cross section polycrystalline nanorod is smaller. The cross section shape have on obvious effect on the deformationmechanism, the deformation mechanism of each model was dominate by the grainboundary sliding.