Molecular dynamics simulation of the tensile mechanical behaviors of axial torsional copper nanorod

The tensile mechanical behaviors of axial torsional copper nanorods with the diameter of 5–6.5 nm are investigated systematically by molecular dynamics simulation. When increasing the angle of torsion loading, the initial stress gradually departures from the near-zero state, and the elastic modulus remains essentially constant. The tensile yield is closely related to the surface deformation reflected by the average potential energy of surface atoms (Pe_Surf). In spite of varied torsion loading, the Pe_Surf of nanorods are promoted to a similar critical level by the torsion and tension, and then fall abruptly indicating the nanorods yield. For the nanorods with [001] orientation in long axis, the rotation loading improves the Pe_Surf at the start of tension and makes dislocation nucleation occur easily, leading to the decline of tensile yield strength. For the [110] orientated nanorods, the Pe_Surf rise induced by the torsion is relatively small and quite close to the range size of the critical level, conducing to the insignificant fluctuation of the tensile yield stress. Meanwhile, lowering the temperature, enlarging the aspect ratio, and shrinking the size can lighten the yield stress descend of [001] orientated nanorods in different extents. At a constant temperature, the Pe_Surf differences between the Pe_Surf at yield moment and initial Pe_Surf without any loadings for all [001] orientated nanorods disperse in a narrow range, no matter how the aspect ratio and size change. This work contributes to understanding the mechanical properties and yield mechanisms of the nanorods under the torsion-tension combined loading.