Electrical conduction in thin lubricating oil films

Under conditions of hydrodynamic lubrication oil forms a thin film between the lubricated surfaces. An investigation of the electrical properties of such films is described, the measurements being made under dynamic conditions. It is shown that the electrical conduction is consistent with space-charge limited current in the presence of a uniform distribution of traps. The oil film is considered to form a pressure-frozen quasi-solid of glass-like material. A rise in current corresponding to the trap-filled limit is observed and imparts a conductivity switching type of behaviour to the film, reminiscent of amorphous glass switching of the Ovshinsky type.