Papers by Alejandro Rodriguez Mendez
Eksploatacja i Niezawodnosc - Maintenance and Reliability, 2016
ASME 2013 Conference on Information Storage and Processing Systems, 2013
Lubricant accumulation on the slider's surface of a hard disk drive (HDD) has a detrimental effec... more Lubricant accumulation on the slider's surface of a hard disk drive (HDD) has a detrimental effect on its read/write performance. Air flow through the slider-disk clearance moves some of the lubricant from the air-bearing surface (ABS) toward the slider's lateral walls where it accumulates. In this article, we show by numerical simulations that the lubricant accumulation characteristics are strongly dependent on the slider's flying height, skew angle and ABS design. The lubricant flow on the slider's surface is quantified numerically. Air shear stress, air pressure and disjoining pressure are used as driving forces in the simulations. The lubricant thickness profile and volume evolution are calculated for two states of the HDD: operating and at rest. In the first state, lubricant is driven by air shear stress toward the trailing edge of the slider where it accumulates on the deposit end. In the second state, lubricant from the deposit end flows back into the ABS driven by the action of disjoining pressure. Lubricant accumulation on the four lateral walls of the slider is taken into account. The lateral walls are unfolded to study the flow using a two-dimensional lubrication model. The effects of flying height, skew angle and slider design on the accumulation removal of lubricant from the ABS are determined for the two states of the drive. Keywords Air bearings Á Lubricant transfer Á Head–disk interface Á Hard disk drive
Effect of various physical factors on thin lubricant film migration on the flying head slider at ... more Effect of various physical factors on thin lubricant film migration on the flying head slider at the head-disk interface of hard disk drives J. Appl. Phys. 102, 054309 (2007); 10.1063/1.2777139 Effect of van der Waals forces on molecularly thin lubricant in the magnetic storage head-disk interface J. Appl. Phys. 98, 124906 (2005); 10.1063/1.2148633 An effect of dewetting of lubricated surfaces on friction and wear properties In heat assisted magnetic recording (HAMR) technology for hard disk drives, the media will be heated to about 500 C during the writing process in order to reduce its magnetic coercivity and thus allow data writing with the magnetic head transducers. The traditional lubricants such as Z-dol and Z-tetraol may not be able to perform in such harsh heating conditions due to evaporation, decomposition and thermal depletion. However, some of the lubricant depletion can be recovered due to reflow after a period of time, which can help to reduce the chance of head disk interface failure. In this study, experiments of lubricant thermal depletion and reflow were performed using a HAMR test stage for a Z-tetraol type lubricant. Various lubricant depletion profiles were generated using different laser heating conditions. The lubricant reflow process after thermal depletion was monitored by use of an optical surface analyzer. In addition, a continuum based lubrication model was developed to simulate the lubricant reflow process. Reasonably good agreement between simulations and experiments was achieved.
In current hard disk drives, the minimum air-bearing clearance is of the order of 1 nm during the... more In current hard disk drives, the minimum air-bearing clearance is of the order of 1 nm during the read/write process. At this ultra-low spacing, lubricant from the disk often transfers to the slider's air-bearing surface imposing a significant degradation of its performance. It is necessary to make accurate predictions of the lubricant's response at the head–disk interface in order to engineer reliable hard disk drives. In this article, we perform numerical simulations to investigate the dewetting behavior of some perfluoropolyether lubricant films used in hard disk drives. We model the lubricant flow on the slider surface using a governing equation based on classical lubrication theory. We consider a disjoining pressure that approximates the properties of a ZTMD lubricant and compare the results with those obtained using a purely van der Waals disjoining pressure. We study the spreading of a lubricant film on a slider both at rest and while flying over a spinning disk. The effect of surface tension, air shear stress, and sub-strate roughness on the dewetting behavior of the film is also investigated.
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Papers by Alejandro Rodriguez Mendez