| The mechanical properties of two kinds of nanometal under different external load are studied by molecular dynamics(MD) simulation, it's based on the analytical embedded atom potential, the effect of temperature,size and strain rate of mechanical properties were studied in detail. It explains the unique mechanical properties of nanometal by studying the strain-stress curve, atomic location map.The simulation results of the body centered of the Mo nanocrystals indicate that:dislocations and slips are main mechanisms of the tension deformation of single Mo naro-wires. From the surface atomic beginning, as the expansion of atomic vacancies are created nano-wire fracture. When the temperature is increased from 100K to 500K, the yield strength and strain decrease, and the fracture strength and strain increase, respectively. The maximum fracture strength is at room temperature (300K). Furthermore, the structures of the stretched nanowires at 100K and 300K have apparent yield deformation and the interior deformation is caused by slips. At 500K, the structures of the stretched nanowires have no apparent yield deformation, and the atomic arrangement of the interior is irregular and disordered and mixed with a large number of dislocations and slips. The simulation results of different sizes show that the strain-stress curves have no obvious deformation in elastic deformation with the sizes increasing. In the yield deformation, size effects have an important role. The region of yield deformation is more and more narrow and the yield strain decrease, the yield strength increasing. In the simulation of strain rate show that the yield and fracture strength will increase with the strain rate increased.The simulation results of face centered nano-Ag wire show that:for single crystal, during the tensile load, slips are the main cause of the inside deformation and appear part of dislocation, forming lots of stows and emergent multiple necking at a distance of top and bottom nanowires about 1\3. during the tension of polycrystalline nanowires, in the elastic deformation stage, the nanowires appear several yield deformation and the stress is the"之"shape up and down with strain increasing. In the plastic deformation, the stress-strain curve increase rapidly as the strain increasing, then there is a fracture yield platform. The nanowire appeared super-plastically as the strain increased.Different structures of nanowires during tensile process indicate that:BCC nanowires go into the elastic deformation earlier than FCC nanowires and BCC nanowires dense low, but it has better scalability. During the elastic deformation and plastic deformation, it has almost equal strain intervals; the yield strength is less than breaking strength, showing greater scalability; relative to the BCC of nanowires, FCC nanowires are based on elastic deformation, however elastic deformation took 1/4 of the entire load strain; during plastic deformation, the atomic model appeare necking quickly and the yield strength greater than the breaking strength.In the deformation of the atomic structure, the nanowires of BCC structure destroy form the surface beginning, the deformation of the atomic model are based on the surface dislocation and internal slip and emergence of a small amount of stacking, finally, the nanowires are necking from the middle of structure and appeared breaking; but the nanowires of FCC structure appeared the vast internal slip of the surface from the beginning, the deformation of the atomic structure are based on slip and finally emergence of dual-necking. |
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