Indentation Curves of Surface Films

Abstract

Various ball indentation curves of thin surface films have been obtained experimentally. The normal contact forces (range 10⁻⁵ — 10N) and the normal displacement (range 1 nm — 1500 nm) between a sphere and a flat plate are continuously investigated during the indentation process. The solids are made in soda-lime or sapphire (Al₂O₃) and covered by natural pollution layers or Polystyrene layers.

The speed of the indentation displacement is kept constant during the experiment. For higher loads (> 0.5 N), the results agree with the classical Hertz theory, but for smaller loads, the disparity is important. The hypotheses proposed in the literature are analyzed: intermolecular forces, surface roughness, mechanical properties of solid surface films.

According to our results, the mechanical properties of surface films connected with adhesion are responsible for the results presented.

Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Tribology Conference in Atlanta, Georgia, October 8–10, 1985

Notes

Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Tribology Conference in Atlanta, Georgia, October 8–10, 1985