Atomic-scale finite-element model of tension in nanoscale thin film

In this paper, a 2D atomic-scale finite-element model of tension in nanoscale thin film is developed in which Morse’s potential energy function is used to model the interactive forces between atoms. The model is fed into the finite-element package LS-DYNA and both a single integration point and an explicit solution method are used for solving the tension process rapidly to investigate the size effect of different film thicknesses and the effect of different atomic vacancy ratios on nanoscale thin film under tension. The results show that since the applied displacement is exerted at both ends for different thickness of a perfect crystal, a neutral line is formed at the middle of the material. The material slides along the easiest slip direction to cause a “necking” feature on both sides. The stress initially increases with the gradual increase of strain and thicker film shows a larger tensile stress. After the film experiences the peak stress, the stress then decreases with the gradual increase of strain. While the applied displacement is applied at both ends for different vacancies, a neutral line is formed at the middle of material, but this is not apparent due to the random scattered vacancies. The material slides along the easiest slip direction from left to right, and the stress concentration areas near the constrained ends form “necking” features. Stresses are not zero at zero strain. Tension tests for different vacancy ratios show different maximum stresses. Film with a larger vacancy ratio shows a lower stress at the same strain. As the vacancy ratio of the film under tension increases, the strength and elastic modulus reduces.