The effect of porosity on the head-media interface

A lubrication model for the head-media interface is presented which include s the effect of porosity in the media coating. Experimental data is shown w hich illustrates the reduction in head-media spacing as porosity is increas ed. A modified Reynolds equation is derived to account for the effects of c oating porosity. Other authors have considered a very thin porous layer to stimulate a liquid lubricant or surface microstructure on a nonporous subst rate. This study considers a porous layer that can be much larger than the bearing clearance. Darcy's law is used in the porous layer. Velocity-slip e ffects, resulting both from rarefaction and the porous boundary, are consid ered. The modified Reynolds equation is applied to a simple capillary model of a porous layer as an illustrative example. The modified Reynolds equati on was incorporated into a finite-element model for the head-media interfac e. Computations show reduced head-media clearance as porosity and permeabil ity are increased in agreement with experimental data.