Yield point phenomena during indentation

The transition from purely elastic to plastic deformation during the initial stages of indentation is explored. The yield point is dependent on crystal orientation, and the extent of the transition from elastic to plastic deformation is compared to a model utilizing a superdislocation to accommodate deformation based on a change in shear stress before and after the yield point. The thickness of an oxide film is shown to impact, but not be solely responsible for, this phenomenon. High dislocation densities limit, and eventually eliminate, the ability to sustain elastic loading. Finally, the yield point is clearly both stress and time dependent; yielding occurs when a tip is held at a constant load over a period of time ranging from seconds to minutes.