Molecular dynamics analysis on bending mechanical behavior of alumina nanowires at different loading rates

The molecular dynamics (MD) model of a-Al2O3 nanowires in bending is established by using LAMMPS to calculate the atomic stress and strain at different loading rates in order to study the effect of loading rate on the bending mechanical behaviors of the a-Al2O3 nanowires. Research results show that the maximum surface stress-rotation angle curves of a-Al2O3 nanowires at different loading rates are all divided into three stages of elastic deformation, plastic deformation and failure, where the elastic limit point can be determined by the curve symmetry during loading and unloading cycle. The loading rate has great influence on the plastic deformation but little on the elastic modulus of a-Al2O3 nanowires. When the loading rate is increased, the plastic deformation stage is shortened and the material is easier to fail in brittle fracture. Therefore, the elastic limit and the strength limit (determined by the direct and indirect MD simulation methods) are closer to each other. The MD simulation result of alpha-Al2O3 nanowires is verified to be valid by the good agreement with the improved loop test results. The direct MD method becomes an effective way to determine the elastic limit and the strength limit of nanoscale whiskers failed in brittle or ductile fracture at arbitrary loading rate.