Research Papers: Micro-Nano Tribology

Analysis of Microwaviness-Excited Vibrations of a Flying Head Slider in Proximity and Asperity Contact Regimes

[+] Author and Article Information
Kyosuke Ono

Tokyo Institute of Technology,
2 Chome-12-1 Ookayama,
Meguro, Tokyo 152-8550, Japan

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received October 7, 2016; final manuscript received February 6, 2017; published online June 15, 2017. Assoc. Editor: Frank Talke.

J. Tribol 139(6), 062001 (Jun 15, 2017) (13 pages) Paper No: TRIB-16-1317; doi: 10.1115/1.4036174 History: Received October 07, 2016; Revised February 06, 2017

The vibration characteristics of a thermal fly-height control (TFC) head slider in the proximity and asperity contact regimes attract much attention, because the head–disk spacing (HDS) must be less than 1 nm in order to increase the recording density in hard disk drives. This paper presents a numerical analysis of the microwaviness (MW)-excited vibrations in the flying head slider during the touchdown (TD) process. We first formulate the total force applied to the TFC head slider as a function of the HDS, based on rough-surface adhesion contact models and an air-bearing force model. Then, the MW-excited vibrations of a single-degree-of-freedom (DOF) slider model at TD are simulated by the Runge–Kutta method. It is found that, when the MW amplitude is less than the spacing range of static instability in the total force, the slider jumps to a contact state from a near-contact or mobile-lubricant-contact state. It then jumps to a flying state even when the head surface is protruded further by increasing the TFC power. When the MW amplitude is relatively large, a drastically large spacing variation that contains a wide range of frequency components below 100 kHz appears in the static unstable region. These calculated results can clarify the mechanisms behind a few peculiar experimental phenomena reported in the past.

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Fig. 1

Rough-surface contact model between the head and the magnetic disk: (a) TFC head–disk contact model and (b) rough-surface contact model

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Fig. 2

Various pressures between flat surfaces when Tbl = 1.0 nm

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Fig. 3

Total pressure between flat surfaces for two total surface pressure models

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Fig. 4

Two-DOF (a) and single-DOF (b) models of a flying head slider

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Fig. 5

Computer-generated MW of the disk surface for a specified RMS value and measured example: (a) calculated examples of the MW waveform and (b) frequency spectrum of the computer-generated MW and measured example

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Fig. 6

Surface force Fs (red line), air-bearing force minus suspension load Fab − Fsus (blue line), and total force (thick black solid line) as functions of d/σa for various static separations ds/σa of the TFC head when the mobile lubricant thickness Tml = 0.2 nm and the air-bearing ratio r = 2: (a) ds/σa = 4, (b) ds/σa = 3, and (c) ds/σa = 2. The total force Ft for Tml = 0.1 nm and 0.3 nm (when r = 2) is plotted using a thin black line and a thick dotted line, respectively. The total force Ft for Tml = 0.2 nm and r = 3 is plotted using a thin dashed line. The thick dashed line indicates the total static force when the static head separation is decreased to a specified value of ds/σa. The values d1 and d2 are the lower and higher stable separations, respectively, when r = 2 and Tml = 0.3 nm.

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Fig. 7

Ft (h), h(t), H(f), and Z(f) when ds = 3.5σa: (a) σm = 0.1 nm and (b) σm = 0.5 nm

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Fig. 8

Ft (h), h(t), H(f), and Z(f) when ds = 3σa: (a) σm = 0.1 nm and (b) σm = 0.5 nm

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Fig. 9

Ft (h), h(t), and H(f) when ds = 2.5σa: (a)σm = 0.1 nm and (b) σm = 0.5 nm

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Fig. 10

Ft (h), h(t), and H(f) when ds = 2.2σa: (a) σm = 0.1 nm and (b) σm = 0.5 nm

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Fig. 11

Ft (h), h(t), and H(f) when ds = 2σa: (a) σm = 0.1 nm and (b) σm = 0.5 nm

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Fig. 12

Ft (h), h(t), and H(f) when ds = 1.7σa: (a) σm = 0.1 nm and (b) σm = 0.5 nm

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Fig. 13

Ft (h), h(t), H(f), and Z(f) for various values of ds/σa when r = 2, Tml = 0.3 nm, and σm = 0.5 nm

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Fig. 14

Ft (h), h(t), and H(f) for various values of ds/σa when r = 3, Tml = 0.2 nm, and σm = 0.5 nm




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