A PARAMETRIC ELASTIC MODEL FOR INDENTATION TESTING OF THIN-FILMS

This paper describes a parametric model designed to predict the true c ontact radius and distance of approach when a spherical indenter is lo aded against a thin film attached to a substrate. The model is elastic , i.e. no plastic deformation within either the film or the substrate is allowed for, and is valid for perfect adhesion between the film and the substrate. Predictions from the model, for soft films on hard sub strates, are compared with experimental measurements, showing generall y good agreement. Predictions are also made for hard films on softer s ubstrates, although no comparison with experiment is made. The use of the model for low load indentation testing is discussed, in particular its value for determining the load levels for which measured material properties are truly those of the film, being independent of the subs trate.