NANO-ASPERITY CONTACT ANALYSIS AND SURFACE OPTIMIZATION FOR MAGNETIC HEAD SLIDER DISK CONTACT/

Ni-P coated Al-Mg (Ni-P) and glass-ceramic (GC) substrates for magneti c recording are measured by an atomic force microscope (AFM) using dif ferent scan sizes and sampling resolution. AFM measurements of the Ni- P and GC surfaces reveal finer and finer details as the sampling inter val decreases and that the GC surface contains more high frequency det ails than the Ni-P surface. A three-dimensional numerical rough surfac e contact model (X. Tian and B. Bhushan, ASME J. Tribol., 118 (1996) 3 3-42) is used to perform contact analysis on the Ni-P and GC surfaces to study the effect of sampling resolution on contact pressure and con tact area. The contact analysis shows that contact pressure increases and contact area decreases as the sampling interval decreases and aspe rity contact starts from plastic deformation, the scale of which depen ds on the different surface topographical structures. The analysis als o shows that a high frequency structure will facilitate plastic deform ation which is not desired for head/disk durability. The stiction in r ough surface contact problem is also considered using a numerical stic tion model (X. Tian and B. Bhushan, J. Phys. D: Appl. Phys., 29 (1996) 163-178). The stiction model is used to highlight how stiction can be assessed by the bearing ratio of a surface and how stiction is affect ed by the skewness of surface height distribution. Stiction analysis o n two GC surfaces with different skewness shows that a surface with po sitive skewness has less stiction. A uniform patterned texture with an optimum number of identical asperities (such as produced by laser tex turing) appears to be an ideal surface.