Head-disk interface contact mechanics for ultrahigh density magnetic recording

Extremely smooth surfaces, high relative speeds, and remarkably low flying heights are required in ultrahigh density magnetic recording. As a conseque nce, higher contact stresses and shear strains can be encountered at the he ad-disk interface (HDI) due to the enhancement of asperity interactions. De tailed knowledge of the damage due to inelastic deformation at asperity mic rocontacts is therefore of paramount importance to the durability of high-p erformance disk drives. A comprehensive elastic-plastic contact analysis fo r the HDI that is based on a realistic surface topography description and a finite element model is presented in this publication. Magnetic head and s mooth and textured rigid disk surfaces were scanned with an atomic force mi croscope (AFM) at various scales in order to determine the corresponding fr actal parameters. Surface topographies equivalent to those of a slider in c ontact with smooth and textured disks were determined from a fractal analys is of the obtained AFM surface images. The equivalent surface corresponding to smooth disk surfaces was incorporated into a finite element model of th e thin-film disk medium to provide a more realistic approximation of the ac tual surface topographies. Simulation results for the contact pressure at a sperity microcontacts and subsurface von Mises equivalent stress, maximum t ensile stress, and equivalent plastic strain are interpreted in terms of th e carbon overcoat thickness and maximum surface interference distance. The evolution of plasticity and likelihood of cracking in the carbon and magnet ic layers of smooth rigid disks are discussed. It is shown that AFM measure ments, fractal surface characterization, and finite element modeling can be combined in contact analyses of layered media possessing realistic surface topographies and mechanical properties typical of engineering components. (C) 2000 Elsevier Science S.A. All rights reserved.