Material compressibility effects for the squeeze of very thin films

The purpose of the present work is the study and clarification of the essen tial role played by the material compressibility of very thin solid layers such as for instance appear in surface force experiments. For the sake of s implicity, attention will be focused on an elastic him squeezed between rig id surfaces. The starting point is the classical lubrication theory reformu lated within the framework of linear elasticity (Incompressible Reynolds Mo del). This model is then extended to include compressibility effects. This extension is based on a phenomenological analysis of the stress and strain Fields obtained in some simple model cases and which are shown to correspon d to an oedometric squeeze inside the contact with boundary corrections. Th is results in the oedometric Reynolds model which is then applied to two sp ecial cases: a uniform film of constant thickness under plane strain condit ion and the interfacial film occurring in the sphere/plane contact. These t wo problems confirm the fact that compressibility cannot be neglected for v ery thin films and show that the governing adimensional parameters combine compressibility and thinness. (C) Elsevier, Paris.