Molecular Dynamics Simulation of Nanoindentation of Gold Substrate: Velocity Effect

Calculating the mechanical properties of small samples is of great importance in Nanotechnology. Nanoindentation is a conventional technique for determining the mechanical properties of materials at small dimensions. This work investigates the dependence of gold behavior during nanoindentation on different indentation velocities by three-dimensional molecular dynamics simulation. A diamond tip with a spherical shape was employed in the simulations and the substrate was made of single crystal Au (100). The temperature of the simulations was fixed at 1 K in order to prevent the gold atoms’ fluctuations. Young’s modulus for the gold was acquired from the load displacement response during a full indentation cycle and compared to those of experiments. The results demonstrated that the critical velocity is observed around 100 m/s, at which the yielding of the sample occurs. For the velocities lower than the critical velocity, higher indentation rates result in increasing the Young’s modulus. However, this trend does not apply to the velocities around the critical value. Finally, by comparing the obtained moduli to the experimental values, we concluded that the moduli from the simulations were higher than the experiments in the macro-scale. We further discussed the origins of this difference.

Keywords:

Nanoindentation , Molecular Dynamics Simulations , Indenter , Young’s modulus