HARDNESS OF THIN-FILM MEDIA - SCRATCH EXPERIMENTS AND FINITE-ELEMENT SIMULATIONS

Experiments and finite element simulations are presented pertaining to the effective hardness and the mechanics of indentation and sliding c ontact on elastic-plastic layered media. Hardness measurements obtaine d from scratch experiments are presented for thin-film rigid disks wit h 30 rzm carbon overcoats. Reproducible results are obtained for resid ual scratch depths greater than approximately 8 nm. A simple force bal ance model is used to calculate the effective hardness of the layered medium. Hardness values for the surface layer are calculated by fittin g a relationship between the hardness, scratch geometry, and layer thi ckness to the experimental data. The experimental results are compared with three-dimensional finite element simulations of a rigid spherica l indenter sliding over a half-space with a stiffer and harder surface layer The finite element results are used to verify the hardness mode l applied to the experimental data and to provide insight into the obs erved experimental behavior in the context of the associated elastic-p lastic deformation characteristics of the layered medium.