Stiffness and Damping of Compressible Lubricating Films Between Computer Flying Heads and Textured Media: Perturbation Analysis Using the Finite Element Method

Abstract

Averaged static and dynamic lubrication equations are derived in the general form containing anisotropic film thicknesses dependent on roughness orientation. Solving these equations lead to a presentation of the dynamic characteristics of lubricating films existing between computer flying heads and textured media. Squeeze effects owing to moving roughness accompanying high-frequency spacing variation are found to be given as a function of arithmetically averaged film thickness minus harmonically averaged film thickness. The calculation procedure using the finite element method is then presented for the averaged static and dynamic lubrication equations. Stiffness and damping coefficient are demonstrated indicating the effects of roughness orientation and roughness movement. Under the fixed static film conditions, the roughness decreases the stiffness. In contrast to this, the roughness only slightly affects the damping coefficient. Under fixed load and loading point conditions, these relationships are inversed. It is interesting to note that damping coefficients are decreased by longitudinal roughness and are increased by moving transverse roughness. The reason for this tendency is considered to be that the moving transverse roughness serves to generate the squeeze damping force.