Dynamic analysis of the rarefaction-modified Reynolds equation consideringporosity of thin liquid lubricant film

A rarefaction-modified Reynolds equation was derived to solve dynamic probl ems of a thin liquid lubricant film coated on a sliding surface. Applying t he perturbation method, a calculation procedure based on FEM was formulated to obtain the stiffnesses and damping coefficients of gas lubricating film s over a permeable liquid lubricant. Calculations were performed for a spec ified flying head slider. First, the effects of the permeability and porosi ty correction coefficients, which serve to increase the molecular mean free path, were presented focusing on landing on/off characteristics. Next, the effects of those on the stiffnesses and damping coefficients were demonstr ated using the frequency domain. The results showed that the permeability a nd porosity correction coefficient increasingly had an influence on the lan ding on/off characteristics more in the higher velocity region, and that th e permeability was effective in increasing the damping of lubricating films .