SIZE EFFECTS ON EFFECTIVE YOUNG'S MODULUS OF NANO CRYSTAL COPPER WIRES

In this paper, a study is made for the size effects on the effective Young's modulus of nano crystal copper wires. On the basis of numerical results of molecular dynamics simulation, the inhomogeneous property of the nano wires is taken into account so that the continuum model of either a rod or a beam is constructed to predict the size dependence of the effective Young's modulus. The comparison with molecular dynamics simulation based on embedded atom method shows that the new rod model enables one to predict the effective Young's modulus as accurately as existing models for the nano wires of different sizes of cross sections under axial load. Furthermore, the beam model gives better prediction than the current model for the nano wires subject to pure bending. The size effect on the elastic property can also be observed from the longitudinal and transverse natural vibration of the nano wires. In this case, the effective Young's modulus is nearly the same as that obtained through axial deformation and pure bending respectively.