Contact analysis of laser textured disks in magnetic head–disk interface

Abstract

Friction and wear behavior of a laser textured disk surface in contact with a magnetic head slider depends on the shape and size of the laser bumps, number of bumps, and mechanical properties of the disk and slider surfaces. In this study, analytical expressions for the height distributions of sombrero- and donut-shaped laser bumps, commonly used in the disk applications, have been developed. These expressions are used to generate the bumps on the computer. Contact analyses of these surfaces are carried out using analytical and numerical methods. Expressions for calculation of meniscus forces for spherical bumps and cylindrical rims are derived. An analytical method is developed to calculate meniscus forces, contact area and optimum number of bumps of a constant height, as a function of bump size and shape to minimize plastic deformation and stiction. A generalized numerical model, developed earlier for random surfaces, is used for contact analysis of bumps with a height distribution. Design curves are generated to estimate optimum number of bumps for a given height distribution, as a function of yield stress of the disk surface. Contact areas (pressure) and meniscus forces of the two bump geometries for a given rim radius and bump height are compared. It is observed that at a given yield stress, donut-shaped bumps result in lower contact area and meniscus force compared to sombrero-shaped bumps.