AFM Imaging, Roughness Analysis and Contact Mechanics of Magnetic Tape and Head Surfaces

[+] Author and Article Information
P. I. Oden

Department of Physics, Arizona State University, Tempe, AZ 85287

A. Majumdar, A. Padmanabhan

Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, AZ 85287

B. Bhushan

I.B.M. Research Division, Almaden Research Center, San Jose, CA 95120

J. J. Graham

STM-Industrial Affiliates Program, Arizona State University, Tempe, AZ 85287

J. Tribol 114(4), 666-674 (Oct 01, 1992) (9 pages) doi:10.1115/1.2920934 History: Received March 07, 1991; Revised June 01, 1991; Online June 05, 2008


Roughness measurements of a magnetic tape, a biaxially oriented poly (ethylene terephthalate) (PET) substrate, a tape head and a rigid-disk slider were made by an atomic force microscope (AFM) and a non-contact optical profiler (NOP). The lateral resolution of the surface topographs ranges from 1 μm (for NOP) down to 1 nm (for AFM). The AFM images show submicron features of the surface that are characteristic of the manufacturing processes. Some of the statistical roughness parameters conventionally used in theories of contact mechanics showed strong dependence on instrument resolution. This suggests that, firstly, roughness measured by NOP at resolutions larger than 1 μm cannot be used to study tribology at sub-micrometer scales and, secondly, a scale-independent characterization by fractal geometry is necessary. Fractal analysis of the tape surface reveals two regimes of roughness demarcated by a scale of 0.1 μm corresponding to the size of magnetic particles. The fractal behavior explains the dependence of the rms height, slope and curvature on the instrument resolution. The predictions of real area of contact suggest that nanometer-scale asperities tend to deform plastically whereas micrometer-scale ones deform elastically.

Copyright © 1992 by The American Society of Mechanical Engineers
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