A study on a rigid body boundary layer interface force model for stress calculation andstress–strain behaviour of nanoscale uniaxial tension

Abstract

A rigid body boundary layer interface force (RIF) model for stress calculation on thenanoscale is proposed in this paper for calculating stress based on molecular dynamics. TheRIF model is used to study the stress–stain behaviour when nanoscale single crystal copperis under uniaxial tension, and is used for 15 tensile simulations each with different strainrate. The stress–strain curve established from simulation was first converted into a truestress–strain curve; a regression analysis was then applied in order to find the flow curve.From simulation results, it is found that the strain rate has large influence on bothK and n values of the flow curve. At low strain rate (less than1 × 1012 s−1),both K and n values decrease with the increase of strain rate. When the strain rate exceeds1 × 1012 s−1, the strain rateagainst the K and n values of the flow curve approaches a constant. Flow curve equations consideringthe influence of strain rate are derived; both complete and simplified forms offlow curve equations are also derived. It is observed that the lower the strainrates, the higher the fluctuations of the stress–strain curve. Furthermore, theincrease of strain rate resulting in a smoother stress–strain curve is also found.