Kinetic Meniscus Model for Prediction of Rest Stiction

1998 ◽  
Vol 120 (1) ◽  
pp. 42-50 ◽  
Author(s):  
B. Bhushan ◽  
C. A. Kotwal ◽  
S. K. Chilamakuri
Keyword(s):  
Static Friction ◽  
Disk Drives ◽  
Equilibrium Time ◽  
Smooth Disk ◽  
Asperity Contacts ◽  
Rest Time ◽  
First Time ◽  
Stationary Contact ◽  
Computer Disk ◽  
Meniscus Model

The time dependence of static friction is an important aspect of tribological studies whereby the static friction increases with an increase in the time of stationary contact (rest static friction or rest stiction). This effect is commonly observed in computer disk drives especially at high humidities, in which the static friction increases rapidly with an increase in rest time between some head slider and the disk surfaces. For the first time, a comprehensive kinetic meniscus model is proposed to explain this phenomenon, both for a single asperity and multiple asperity contacts at a liquid mediated interface. It is found that the static friction increases up to a certain equilibrium time with a power law relationship after which it remains constant. The equilibrium time is dependent on the liquid film thickness, the liquid viscosity and the contact geometry. The model developed is applied to a rough textured disk, a polished disk and a super smooth disk. To study the effect of the scan size on the meniscus force, the static friction is calculated by using roughness parameters obtained from measurements at different scan sizes.

Experimental Study of Stationary Head-Disk Contact in Magnetic Disk Drives

1993 ◽  
Vol 115 (2) ◽  
pp. 214-218 ◽  
Author(s):  
N. V. Gitis ◽  
R. Sonnenfeld
Keyword(s):  
Thin Film ◽  
Static Friction ◽  
In Situ Monitoring ◽  
Disk Drives ◽  
Magnetic Disk ◽  
Surface Separation ◽  
Disk Contact ◽  
Force Increase ◽  
Stationary Contact

Magnetic disk drives are vulnerable to “stiction” a contact phenomenon in which static friction greatly exceeds kinetic friction. Stiction tends to increase dramatically with time of stationary contact. Thus, processes leading to stiction in the stationary head-disk contact are an important subject of tribological studies. Measurements of the static friction force are accompanied in this work by measurements of the capacitance between a resting slider and a thin-film rigid disk. Capacitance provides a sensitive measure of the surface separation and allows in-situ monitoring of the stationary contact. The experiments have shown that if the disk is covered with a thin film of a mobile lubricant, the adhesion growth with time measurably pulls the slider nearer to the plane of the disk (“slider microdescent”), and both the stiction and capacitance increase. If there is no mobile lubricant film, there is no growth of either stiction or capacitance. Thus, the stiction phenomenon is connected strongly with the slider microdescent. Their time dependence is likely governed by the capillary force increase caused by redistribution of the mobile lubricant toward the newly formed menisci.

ELECTROSTATIC DISCHARGE EFFECT ON TMR RECORDING HEAD: A FLEX ON SUSPENSION CAPACITANCE APPROACH

2009 ◽  
Vol 23 (17) ◽  
pp. 3586-3590 ◽  
Author(s):  
NUTTACHAI JUTONG ◽  
APIRAT SIRITARATIWAT ◽  
DUANGPORN SOMPONGSE ◽  
PORNCHAI RAKPONGSIRI
Keyword(s):  
Human Body ◽  
Electrostatic Discharge ◽  
Hard Disk Drives ◽  
Electrical Characteristics ◽  
Disk Drives ◽  
Human Body Model ◽  
Recording Head ◽  
Body Model ◽  
Recording Heads ◽  
First Time

Electrostatic discharge (ESD) effects on GMR recording heads have been reported as the major cause of head failure. Since the information density in hard-disk drives has dramatically increased, the GMR head will be no longer in use. The tunneling magnetoresistive (TMR) read heads are initially introduced for a 100 Gbit/in2 density or more. Though the failure mechanism of ESD in GMR recording heads has not been explicitly understood in detail, a study to protect from this effect has to be done. As the TMR head has been commercially started, the ESD effect must be considered. This is the first time that the TMR equivalent circuit has been reported in order to evaluate the ESD effect. A standard human body model (HBM) is discharged across R+ and R- where the capacitances of flex on suspension (FOS) are varied. It is intriguingly found that the electrical characteristics of the TMR head during the discharge period depend on the discharge position. This may be explained in terms of the asymmetry impedance of TMR by using adapted Thevenin's theory. The effect of FOS components on TMR recording heads is also discussed.

On the Static-Kinetic Friction Transition in Dry Contact of Rough Surfaces

2011 ◽  
Author(s):  
K. Farhang ◽  
D. Segalman ◽  
M. Starr
Keyword(s):  
Large Scale ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Static Friction ◽  
Partial Slip ◽  
Small Scale ◽  
Asperity Contact ◽  
Kinetic Friction ◽  
Tangential Load ◽  
Asperity Contacts

This paper shows that the Mindlin problem involving two spheres in contact under the action of oscillating tangential force can lead to the account of static-kinetic friction transition. In Mindlin’s problem two spheres experience partial slip as a result of application of oscillating tangential load. When the problem is extended to multi-sphere contact, i.e. two rough surfaces, the application of tangential oscillating load results in partial slip for some asperity contacts while others experience full slip. Increase in the amplitude of the oscillating tangential force results in more contacts experiencing full slip, thereby decreasing the number of contacts in parial slip. Constitutive relation proposed by Mindlin at small scale, governing asperity interaction, is used to obtain the large scale slip function through a statistical summation of asperity scale events. The slip function establishes the fraction of asperity contact in full slip. The complement of the slip parameter is a fraction of asperities in partial slip. Through slip function it is shown that it is possible to define a slip condition for the entire surface. The derivation of the slip function allows the account of transition between static friction and kinetic friction.

Combined finite element-boundary element method modelling of elastic multi-asperity contacts

2009 ◽  
Vol 223 (5) ◽  
pp. 767-776 ◽  
Author(s):  
S Ilincic ◽  
G Vorlaufer ◽  
P A Fotiu ◽  
A Vernes ◽  
F Franek
Keyword(s):  
Finite Element ◽  
Boundary Element Method ◽  
Boundary Element ◽  
Hertzian Contact ◽  
Multilayer Systems ◽  
Influence Coefficients ◽  
Asperity Contacts ◽  
First Time ◽  
Element Algorithm ◽  
Element Method

A novel formulation of elastic multi-asperity contacts based on the boundary element method (BEM) is presented for the first time, in which the influence coefficients are numerically calculated using a finite element method (FEM). The main advantage of computing the influence coefficients in this manner is that it makes it also possible to consider an arbitrary load direction and multilayer systems of different mechanical properties in each layer. Furthermore, any form of anisotropy can be modelled too, where Green's functions either become very complicated or are not available at all. The rest of the contact analysis is then performed applying a custom-developed boundary element algorithm. The scheme was tested by considering the frictionless contact between a flat surface and a sphere. The obtained results are in good agreement with the analytical solution known for a Hertzian contact. Applied to either a frictionless or a frictional contact between real surfaces of different samples, our FEM-BEM method has shown that the composite roughness of surfaces in contact uniquely determines the contact pressure distribution.

Particle detachment from disk surfaces of computer disk drives

1991 ◽  
Vol 22 (6) ◽  
pp. 737-746 ◽  
Author(s):  
Chuen-Jinn Tsai ◽  
David Y.H. Pui ◽  
Benjamin Y.H. Liu
Keyword(s):  
Disk Drives ◽  
Particle Detachment ◽  
Computer Disk

MEASUREMENT OF THE STATIC FRICTION COEFFICIENT BETWEEN A poly-V belt 5pk AND A PULLEY UNDER DRY CONDITIONS

Tribologia ◽  
2018 ◽  
Vol 277 (1) ◽  
pp. 57-62
Author(s):  
Krzysztof KUBAS
Keyword(s):  
Friction Coefficient ◽  
Nonlinear Function ◽  
Static Friction ◽  
Friction Forces ◽  
Good Accordance ◽  
Dry Conditions ◽  
Rest Time ◽  
Wrap Angle ◽  
Different Shapes ◽  
Static Coefficient

The paper presents the results of experimental measurements of static friction forces between a poly-V belt 5pk and a pulley on a specialised research stand. An average effective static coefficient is assumed depending on the wrap angle and preload force. Different shapes and positions of curves of the measured values for lower wrap angles are found, with similar curves in the set of measurements with higher angles. The Nelder-Mead optimisation method is proposed to approximate the measured results by a nonlinear function and to achieve good accordance. The dependence of the effective friction coefficient on the rest time between measurements is also presented.

Optimal Sliding Mode Dual-Stage Actuator Control in Computer Disk Drives

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Seung-Hi Lee
Keyword(s):  
Discrete Time ◽  
Sliding Mode ◽  
Voice Coil Motor ◽  
Disk Drives ◽  
Flexible Mode ◽  
Control Scheme ◽  
Dual Stage ◽  
Actuator Control ◽  
Dual Stage Actuator ◽  
Computer Disk

This paper presents a discrete-time design of a dual-stage actuator control system with sliding mode for computer disk drives. A state estimator based discrete-time boundary layer sliding mode control scheme is developed for a dual-stage actuator, which consists of a voice coil motor and a microactuator. Considering dominant microactuator flexible mode dynamics and the interaction between the two actuators, an optimal sliding hyperplane is designed to maximize their cooperation so as to attain desired responses. An application example demonstrates the utility of the proposed sliding mode dual-stage actuator control scheme for track-seek in the microactuator range, settle, and track-follow.

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