Time-dependent Nanoindentation

Abstract

In general, materials can resist deformation in a solid-like or viscous-like manner. Solid-like materials store energy under deformation, and upon removal of stress, returns to its original state. Viscous materials dissipate energy during deformation and upon removal of stress, remains in its deformed state. Materials with combined solid-like and viscous-like properties are said to be viscoelastic. Nanoindentation can be used to quantitatively determine the viscoelastic properties of materials. In one method, a small oscillatory force or displacement is imparted to the indenter. The resulting load and displacement signals provide a method whereby the elastic and viscous components of the specimen response can be calculated. In another method, the load or displacement is held at a fixed value and the change in displacement (creep) or load (relaxation) recorded over a period of time. Application of an appropriate mechanical model can yield values for the elastic and viscous properties of the specimen.