MoA-2-4 ANALYSIS OF MICROWAVINESS-EXCITED VIBRATION OF A FLYING HEAD SLIDER IN ASPERITY CONTACT REGIME

2015 ◽  
Vol 2015 (0) ◽  
pp. _MoA-2-4-1-_MoA-2-4-3
Author(s):  
Kyosuke Ono
Keyword(s):  
Asperity Contact ◽  
Head Slider ◽  
Excited Vibration

Improved Analysis of Unstable Bouncing Vibration and Stabilizing Design of Flying Head Slider in Near-Contact Region

2006 ◽  
Vol 129 (1) ◽  
pp. 65-74 ◽  
Author(s):  
Kyosuke Ono ◽  
Masami Yamane
Keyword(s):  
Parametric Study ◽  
Contact Region ◽  
Disk Surface ◽  
Design Guidelines ◽  
Flying Height ◽  
Asperity Contact ◽  
Adhesion Forces ◽  
Characteristic Model ◽  
Head Slider ◽  
Contact Characteristic

This paper describes an improved analytical study of the bouncing vibration of a flying head slider in the near-contact region and gives quantitative designs guideline for realizing a stable flying head slider, based on the results of a parametric study. First, we numerically calculated the general characteristics of the contact and adhesion forces between a smooth contact pad and disk surface by considering asperity contact, the lubricant meniscus, and elastic bulk deformation. As a result, it was shown that the contact characteristics can be represented by a simple model with five independent parameters when the asperity density is large and the asperity height is small as in cases of current slider and disk surfaces. Then, we numerically computed the slider dynamics in a two degree of freedom slider model with nonlinear air-bearing springs by using the simplified contact characteristic model. As a result, we have obtained a self-excited bouncing vibration whose frequency, amplitude and touchdown/takeoff hysteresis characteristics agree much better with the experimental results compared with our previous analysis. From a parametric study for takeoff height, we could obtain design guidelines for realizing a stable head slider in a low flying height of 5nm or less.

Analysis of Microwaviness-Excited Vibrations of a Flying Head Slider in Asperity Contact Regime

2016 ◽  
Author(s):  
Kyosuke Ono
Keyword(s):  
Hard Disk Drives ◽  
Adhesive Contact ◽  
Flying Height ◽  
Design Parameters ◽  
Lubricant Layer ◽  
Asperity Contact ◽  
Head Slider ◽  
Spacing Variation ◽  
Parameter Values ◽  
Fly Height

The flying height of a head slider in hard disk drives has been decreased close to 1 nm but still must be reduced to ∼0.5 nm in order to increase recording density. At such a narrow spacing, variation in head/disk spacing caused by microwaviness (MW) becomes a significant concern [1]. Some comprehensive numerical simulations of slider dynamics in the near-contact and contact regimes have been conducted [2–5]. However, the real physics behind slider dynamics does not seem to be fully elucidated because the head-disk interfacial force changes with differences in interfacial design conditions such as the air-bearing surface, surface roughness, and lubricant layer. In this study, we evaluated head-disk interfacial forces by asperity adhesive contact theories with measured asperity parameter values. The MW-excited vibrations of a thermal fly-height control (TFC) slider in proximity and asperity contact regimes were simulated by changing the design parameters. It was found that the simulated results allow us to understand typical experimental results reported in previous literature.

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

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Kyosuke Ono
Keyword(s):  
Hard Disk Drives ◽  
Force Model ◽  
Total Force ◽  
Asperity Contact ◽  
Contact State ◽  
Head Slider ◽  
Adhesion Contact ◽  
Head Surface ◽  
Wide Range ◽  
Spacing Variation

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.

scholarly journals Contact stiffness and damping of spiral bevel gears under transient mixed lubrication conditions

Friction ◽  
2021 ◽  
Author(s):  
Zongzheng Wang ◽  
Wei Pu ◽  
Xin Pei ◽  
Wei Cao
Keyword(s):  
Contact Stiffness ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Spiral Bevel Gears ◽  
Bevel Gears ◽  
Dry Contact ◽  
Spiral Bevel ◽  
Stiffness And Damping ◽  
Lubrication Conditions ◽  
Film Lubrication

AbstractExisting studies primarily focus on stiffness and damping under full-film lubrication or dry contact conditions. However, most lubricated transmission components operate in the mixed lubrication region, indicating that both the asperity contact and film lubrication exist on the rubbing surfaces. Herein, a novel method is proposed to evaluate the time-varying contact stiffness and damping of spiral bevel gears under transient mixed lubrication conditions. This method is sufficiently robust for addressing any mixed lubrication state regardless of the severity of the asperity contact. Based on this method, the transient mixed contact stiffness and damping of spiral bevel gears are investigated systematically. The results show a significant difference between the transient mixed contact stiffness and damping and the results from Hertz (dry) contact. In addition, the roughness significantly changes the contact stiffness and damping, indicating the importance of film lubrication and asperity contact. The transient mixed contact stiffness and damping change significantly along the meshing path from an engaging-in to an engaging-out point, and both of them are affected by the applied torque and rotational speed. In addition, the middle contact path is recommended because of its comprehensive high stiffness and damping, which maintained the stability of spiral bevel gear transmission.

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