Role of Mechanical Properties and Surface Texture in the Real Area of Contact of Magnetic Rigid Disks

Abstract

The analysis of real area of contact for particulate and thin-film rigid disks is presented. The mechanical properties (hardness and modulus) of the disk structure are measured by a nanoindentation apparatus and the surface texture is measured by a three-dimensional noncontact optical profiler. For typical rigid disks selected for this study, we find that most contacts are elastic; the same observation was made by Bhushan (1984) for flexible media. In the case of elastic contacts, the real area of contact is governed by the effective elastic modulus of the disk structure and its surface summit distribution. Typical values for the fractional real area of contact, number of contacts per unit area, mean asperity diameter, and mean real pressure for a thin-film disk are calculated to be of the order of 5 × 10−5, 20/mm2, 1μm, and 200 MPa, respectively.