Comparison of the static friction subboundary lubrication model with experimental measurements on thin-film disks

Results from a subboundary lubrication (SBL) model for calculating the static friction coefficient of contacting real surfaces in the presence of very thin liquid films are compared with published static friction measurements performed on different magnetic storage hard disks. Four levels of surface roughness repeated by the standard deviation of surface heights sigma and by the GW plasticity index psi are studied, ranging from sigma = 43.1 nm (psi = 1.15) for the roughest surfaces to sigma = 2.95 nm (psi = 0.39) for the smoothest surfaces. In all four cases, good correlation is obtained between the model and the experimental results, suggesting that the subboundary lubrication model is a reliable model which accounts for the main parameters that influence stiction in thin-film disks. A critical film thickness of the lubricant, above which the static friction coefficient increases sharply (stiction), is predicted by the model in agreement with the experiments. A physical examination of the stiction phenomenon in relation to the SBL model, is offered.