The Role of Relative Humidity, Surface Roughness and Liquid Build-Up on Static Friction Behavior of the Head/Disk Interface

1993 ◽  
Vol 115 (1) ◽  
pp. 28-35 ◽  
Author(s):  
Hong Tian ◽  
Takeo Matsudaira
Keyword(s):  
Surface Roughness ◽  
Relative Humidity ◽  
Static Friction ◽  
Height Distribution ◽  
Head Disk Interface ◽  
Friction Behavior ◽  
Friction Forces ◽  
Disk Interface ◽  
Percent Relative Humidity

Stiction at the head/disk interface has become one of the major concerns as smoother surfaces are required to achieve lower flying heights of magnetic heads over magnetic disks. In this paper, static friction forces on three types of disk samples with different surface roughness values were measured at various relative humidities. It was found that static friction coefficients were well correlated with total thickness of liquid (lubricant and adsorbed water) at the head/disk interface. The experimental data also agreed fairly well with the calculated values based on a proposed stiction model. It is implied in the stiction model that the bearing ratio or the shape of asperity height distribution, especially the part of high asperities, determines the stiction force. Moreover, long-term stiction was investigated on the unlubricated disk surfaces at 80 percent relative humidity and on the lubricated disks at 5 percent relative humidity to separate the effects of water build-up and lubricant build-up at the head/disk interface. It appears that long-term stiction occurs only when enough mobile lubricant is present and the thickness of liquid at the head/disk interface is close to a critical thickness value which is related to surface roughness values.

Investigation of Bias Voltage and Relative Humidity on Wear and Pit Formation at the Head–Disk Interface

2020 ◽  
Vol 56 (5) ◽  
pp. 1-7
Author(s):  
Tan D. Trinh ◽  
Christoph Schade ◽  
Michael Johnson ◽  
Frank E. Talke
Keyword(s):  
Relative Humidity ◽  
Bias Voltage ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Pit Formation

Effect of Head–Disk Interface Biasing and Relative Humidity on Wear of Thermal Flying Height Control Sliders

2017 ◽  
Vol 65 (2) ◽  
Author(s):  
Liane M. Matthes ◽  
Frederick E. Spada ◽  
Andrey Ovcharenko ◽  
Bernhard E. Knigge ◽  
Frank E. Talke
Keyword(s):  
Relative Humidity ◽  
Flying Height ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Height Control ◽  
Thermal Flying Height Control

Head-Disk Interface Issues for Near Contact Recording

2001 ◽  
Author(s):  
R. H. Wang ◽  
V. Raman ◽  
U. V. Nayak
Keyword(s):  
Ambient Pressure ◽  
Disk Drive ◽  
Flying Height ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Magnetic Spacing ◽  
Wear And Corrosion ◽  
Disk Lubricant ◽  
Contact Recording

Abstract As the magnetic recording density increases towards hundreds of Gb/in2, both the magnetic spacing and head-disk clearance decrease to < 10 nm. By one estimate, the magnetic spacing for 1 Tb/in2 is about 6 nm and the read width is ∼ 30 nm. There are at least two different approaches to achieving this. The first one is an extension of the traditional flying interface and the second is contact recording. In the former case one needs to be concerned about maintaining adequate clearance both at sea level and at higher elevation whereas in the latter case the wear and corrosion of the heads and disks may pose major challenges. In the flying regime, an accelerated test to assess the relative integrity of the head-disk interface is described here. This is accomplished by monitoring the acoustic emission, capacitance or friction between the head and the disk as the ambient pressure is reduced. The pressure at which an abrupt change in the above signals takes place is called take-off pressure (TOP). This is also known as altitude avalanche measurement. With this method it is possible to compare different disk and head designs at the full velocity of the slider. We present results correlating the TOP with disk roughness and the influence of disk lubricant. An example of how head-disk interference takes place in a disk drive will be given for an experimental 10 nm flying slider. The effects of radial flying height profile, take-off height of the disk, and the disk curvature on mechanical spacing are presented. The results of changes occurring on the air bearing surface and the disks after long term flyability test are discussed.

Tribological Characteristics of Liquid Lubricant on Magnetic Disks Treated by Far-UV Radiation

1993 ◽  
Vol 115 (3) ◽  
pp. 400-405 ◽  
Author(s):  
Hong Tian ◽  
Takeo Matsudaira
Keyword(s):  
Slip Model ◽  
Head Disk Interface ◽  
Rotating Disks ◽  
Magnetic Disks ◽  
Disk Interface ◽  
Liquid Lubricant ◽  
Long Period ◽  
Irradiation Treatment ◽  
Temperature Environment

In this paper, we have shown that a perfluoropolyether lubricant after far-UV irradiation treatment proposed by Saperstein and Lin (1990) was strongly bonded to disk surfaces without depletion from disks rotating at 6000 rpm in a 50°C temperature environment. Nonbonded lubricant (mobile lubricant) on disk surfaces or on the top of the UV-fixed lubricant was easily depleted from rotating disks. Depletion data of the mobile lubricant agreed well with predictions of an inter-slip model. It has been demonstrated experimentally that the mobile lubricant on disk surfaces was simply displaced from the contact or the sliding regions. After a long period of head contact, the lubricant was built up at the head/disk interface due to migration of the mobile lubricant around the contact regions. By contrast, no such build-up was observed for disks with the UV-fixed lubricant. Consequently, long-term stiction was observed for disks with only mobile lubricant, while no stiction was observed for disks with the UV-fixed lubricant. The UV-treated disks also adsorbed less water at high relative humidities compared with the nontreated disks.

Application of Elastic-Plastic Static Friction Models to Rough Surfaces With Asymmetric Asperity Distribution

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Chul-Hee Lee ◽  
Melih Eriten ◽  
Andreas A. Polycarpou
Keyword(s):  
Surface Roughness ◽  
Static Friction ◽  
Contact Forces ◽  
Height Distribution ◽  
Normal Contact ◽  
Elastic Plastic ◽  
Friction Models ◽  
Pearson Distributions ◽  
Asperity Distribution ◽  
Different Levels

Asymmetric height distribution in surface roughness is important in many engineering surfaces, such as in constant velocity (CV) joints, where specific manufacturing processes could result in such surfaces. Even if the initial surfaces exhibit symmetric roughness, the running-in and sliding processes could result in asymmetric roughness distributions. In this paper, the effect of asymmetric asperity height distribution on the static friction coefficient is investigated theoretically and experimentally. The asymmetry of the surface roughness is modeled using the Pearson system of frequency curves. Two elastic-plastic static friction models, the Kogut–Etsion (KE) and Cohen–Kligerman–Etsion (CKE) models are adapted to account for asymmetric roughness and employed to obtain the tangential and normal contact forces. Static friction experiments using CV joint roller and housing surfaces, which exhibit different levels of surface roughness, were performed and directly compared with the KE and CKE static friction models using both a symmetric Gaussian as well as Pearson distributions of asperity heights. It is found that the KE model with the Pearson distribution compares favorably with the experimental measurements.

Effect of environmental humidity on the friction/stiction and durability of lubricated magnetic thin-film disks

1997 ◽  
Vol 211 (4) ◽  
pp. 295-301 ◽  
Author(s):  
Z Zhao ◽  
B Bhushan
Keyword(s):  
Static Friction ◽  
High Humidity ◽  
Head Disk Interface ◽  
Magnetic Thin Film ◽  
Low Friction ◽  
Disk Interface ◽  
Environmental Humidity ◽  
High Durability ◽  
Lubricant Films ◽  
Different Levels

Drag and CSS (contact start and stop) tests were conducted to study the effects of the degree of chemical bonding of the lubricant and environmental humidity on the friction/stiction and durability of the head-disk interface. Disks with untreated, partially bonded and fully bonded films of a polar perfluoropolyether lubricant were tested at different levels of humidity. Static friction is low for unlubricated disks and disks with a fully bonded lubricant film as compared to disks with untreated and partially bonded lubricant films. Static friction gradually increases with an increase in the relative humidity and the effect of humidity at high humidity values is more pronounced in the case of disks with untreated and partially bonded lubricant films. At high humidities, durability is low for all lubricated disks but is high for unlubricated disks, as compared to that at low humidities. At low humidities, durability in drag tests is more sensitive to the degree of bonded fraction than that in the CSS tests. In general, partially bonded lubricant films are desirable for low friction/stiction and high durability and lubricated disks perform best at low to moderate humidities. Operation at high humidities must be avoided.

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