Molecular dynamics evaluation of strain rate and size effects on mechanical properties of FCC nickel nanowires

Based on molecular dynamics method, an atomistic simulation scheme for damage evolution and failure process of nickel nanowires is presented, in which the inter-atomic interactions are represented by employing the modified embedded atom potential. Extremely high strain rate effect on the mechanical properties of nickel nanowires with different cross-sectional sizes is investigated. The stress-strain curves of nickel nanowires at different strain rates subjected to uniaxial tension are simulated. The elastic modulus, yield strength and fracture strength of nanowires at different loading cases are obtained, and the effect of strain rate on these mechanical properties is analyzed. The numerical results show that the stress-strain curve of metallic nanowires under tensile loading has the trend identical to that of routine polycrystalline metals, and the yield strain of nanowires is independent of the strain rate and cross-sectional size. Based on the simulation results, a set of quantitative prediction formulas are obtained to describe the strain rate sensitivity of nickel nanowires on the mechanical properties, and the resulting formulas of the Young's modulus, yield strength and fracture strength of nickel nanowires exhibit a linear relation with respect to the logarithm of strain rate. Furthermore, some comprehensive correlation equations revealing both the strain rate and size effects on mechanical properties of nickel nanowire are proposed through the numerical fitting and regression analysis, and the mechanical behaviors observed in this study are consistent with those from the experimental and available numerical results.