The failure of fluid film at nano-scale

The determination of hydrodynamic film failure has become one of the key as pects in the study of thin film lubrication (TFL) since the hydrodynamic ef fect of fluid film at nano-scale carl be observed with recently developed e xperimental techniques. In the present paper; the relative optical interfer ence intensity (ROII) technique with a resolution of 0.5 run in the vertica l direction has been used to measure the film thickness. Experimental resul ts show that the hydrodynamic effect cart be clearly observed even at very low speed if the contact pressure is sufficiently low or if the viscosity o f lubricant is comparatively high. When the pressure increases to a certain degree, the film will suddenly drop to the dimension of several layers of molecules and this is where the failure of the fluid film has taken place. For different viscosity of lubricants, the fluid film failure occurs at dif ferent rolling speeds and pressures. In addition, when the normal load beco mes higher. a higher speed or larger viscosity is required to form the flui d film in the contact region. Finally, the effects of pressure, viscosity a nd velocity on the occurrence of fluid film failure have been examined and a relationship involving the three parameters is proposed.