Experimental and theoretical evaluation of friction at contacting magnetic storage slider–disk interfaces

Abstract

To understand better the friction force and wear processes at contacting slider-disk interfaces, we have developed an experimental method for measuring and a theoretical method for calculating the friction force. For this study, a slider with a 1500 lm 2 contact pad located at the recording head is burnished against a relatively rough disk ( $ 12 Å rms), which ensures smooth sliding. In the experimental method, the friction force is measured as the disk is spun-down to bring the slider-disk interface into an increasing degree of contact. A modified air bearing code is used to determine the experimental normal contact force for each friction measurement. In the theoretical method, the friction force and other relevant interfacial forces are calculated using an improved sub-boundary lubrication (ISBL) rough surface model. The friction force calculation in this model is based on the force needed to induce yielding of the individual disk asperities contacting the flat surface of the contact pad without any assumption of the coefficient of friction. Good agreement is found between the measured and theoretical friction vs. normal contact force curves, indicating that the model is capturing the essential origins of friction at this interface. The model also provides valuable insights into how wear particles may be generated at this contacting slider-disk interface.

Modeling Sliding Contact of Rough Surfaces with Molecularly Thin Lubricants

“…The presence of lubricant effectively decreases the net clearance between two rough surfaces by an amount t and, more significantly, results in smaller resistance to shear within lubricant contact. Hence, it can be said that the disk lubricant effectively reduces the strength of contact junctions as was found in experiments [6].…”

“…This model is coupled with an existing rough surface dynamic contact model with friction [3,4] that has been extended to include variable lubricant surface energy according to recent experimental measurements [5,6]. Customarily, MTL contact has been neglected in rough surface contact models by assuming that the lubricant is readily displaced upon contact.…”

“…Hence, an adhesion formulation for non-contacting and lubricant contacting asperities-in the context of a Greenwood-Williamson (GW) formulation of roughnessis presented in this work that accounts for variations in the surface energy. MTL layer contact with variable surface energy is combined with the ISBL contact model with friction [3,4] into the proposed MTL dynamic contact model, which is discussed in correlation to available experimental data [5,6].…”

Improved Elastic Contact Model Accounting for Asperity and Bulk Substrate Deformation

“…Nevertheless, as shown for example by McCool [9], allowing multi-scale roughness (different radii of curvature of asperities) does not significantly change the simpler results of the original GW model. Also, despite the known limitations of the GW model, researchers have shown that the GW-based contact model gives good correlation with experiments [10,11].…”

Electrostatically Tunable Adhesion in a High Speed Sliding Interface

“…Maintaining good tribological properties such as low wear and stiction of such a high speed sliding interface at low clearance is critical for the long term reliability of hard disk drives [7]. Any contact between the head and the disk leads to friction and wear of the head overcoat layer, adversely impacting the disk drive performance [8][9][10][11].A unique way of reducing the friction during contact is through externally imposed oscillations of small amplitude and energy. Previous experimental and theoretical work to reduce the friction at a sliding interface explored the use of external excitation with either surface acoustic waves or electrostatic forces to modulate the out-of-plane or in-plane motion [12][13][14][15].…”