A lubrication model for the head-media interface is presented which includes the effect of porosity in the media coating. Experimental data is shown which illustrates the reduction in head-media spacing as porosity is increased. A modified Reynolds equation is derived to account for the effects of coating porosity. Other authors have considered a very thin porous layer to simulate a liquid lubricant or surface microstructure on a nonporous substrate. 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 effects, resulting both from rarefaction and the porous boundary, are considered. The modified Reynolds equation is applied to a simple capillary model of a porous layer as an illustrative example. The modified Reynolds equation was incorporated into a finite-element model for the head-media interface. Computations show reduced head-media clearance as porosity and permeability are increased in agreement with experimental data.

Issue Section:
Technical Papers
Keywords:
magnetic disc storage, magnetic heads, interface phenomena, mechanical contact, rough surfaces, tribology, lubrication, coatings, porous materials, shear flow
Topics:
Coatings, Permeability, Porosity, Porous materials, Pressure, Bearings, Surface roughness, Finite element model, Lubrication, Flow (Dynamics), Lubricants
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