Stiffness and Damping of Thin PFPE Lubricant Bridging Between Magnetic Disk and Diamond Probe Tip

2007 ◽  
Vol 129 (4) ◽  
pp. 720-728 ◽  
Author(s):  
Yasunaga Mitsuya ◽  
Yasuji Ohshima ◽  
Hedong Zhang ◽  
Kei Aoyama ◽  
Toshiyuki Kawai ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Disk Surface ◽  
Spring Constant ◽  
Damping Coefficient ◽  
Curvature Radius ◽  
Magnetic Disk ◽  
Pfpe Lubricant ◽  
Stiffness And Damping ◽  
Diamond Probe ◽  
Spring Constants

Spring constants and damping coefficients of a thin lubricant bridge of a perfluoropolyether (PFPE) lubricant intervening between a diamond probe tip and a diamond-like carbon (DLC) surface of a magnetic disk are identified through regression analysis of tip damping vibration. PFPE lubricants with functional end groups were used to form a lubricant bridge between the DLC surface and a probe tip with a notably small curvature radius of 0.1μm. The tip was both retracted from and extended toward the disk surface at four different progressive distances to attain varied elongation of the bridge. It was also vibrated at each step to provide damping waveforms. By applying regression analysis to the observed waveforms, the spring constant and the damping coefficient of the lubricant bridge were identified within an elongation range from 50nm to 800nm. Spring constant of the lubricant bridge kb had a negative value varying from −0.15N∕m to −0.1N∕m. The damping value expressed in the form of frequency-multiplied damping cb×ω ranged from 0.02N∕m to 0.06N∕m. Note that both the absolute value of spring constant ∣kb∣ and frequency-multiplied damping cb×ω exhibited U-shaped variation with lubricant bridge elongation; that is, those values decrease with bridge elongation and they begin to increase after reaching the minimum. The variation in the spring constant was found to be in good accordance with the quasi-static stiffness of the lubricant bridge, and variation in the damping coefficient was explained by energy loss arising in the vibrating lubricant bridge.

Stiffness and Damping of Molecularly Thin PFPE Lubricant Bridging Between Magnetic Disk and Diamond Probe Tip

2005 ◽  
Author(s):  
Yasunaga Mitsuya ◽  
Yasuji Ohshima ◽  
Hedong Zhang ◽  
Kei Aoyama ◽  
Toshiyuki Kawai ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Liquid Bridge ◽  
Disk Surface ◽  
Spring Constant ◽  
Curvature Radius ◽  
Magnetic Disk ◽  
Pfpe Lubricant ◽  
Stiffness And Damping ◽  
Diamond Probe ◽  
Spring Constants

Spring constants and damping coefficients of a molecularly thin liquid bridge of PFPE lubricant intervening between a diamond probe tip and diamond like carbon (DLC) surface of a magnetic disk are identified through regression analysis of tip damping vibration. Perfluoropolyether (PFPE) lubricants having functional end groups were used to form the liquid bridge between the DLC surface and a probe tip with the notably small curvature radius of 0.1 μm. The tip was both retracted from and extended toward the disk surface at four different, progressive distances to attain varied elongation of the bridge, and was made to vibrate at each step to provide damping waveforms. By applying regression analysis to observed waveforms, the spring constant and the damping coefficient of the liquid bridge were identified. It is interesting to note that both the absolute value of the spring constant and the frequency-multiplied damping decrease with bridge elongation, and after reaching the minimum, those values begin to increase.

scholarly journals Stiffness and Damping of Molecularly Thin PFPE Lubricant Bridging between Magnetic Disk and Diamond Probe Tip

2005 ◽  
Vol 71 (704) ◽  
pp. 1368-1375
Author(s):  
Yasunaga MITSUYA ◽  
Yasuji OHSHIMA ◽  
Hedong ZHANG ◽  
Kei AOYAMA ◽  
Toshiyuki KAWAI ◽  
...  
Keyword(s):  
Magnetic Disk ◽  
Pfpe Lubricant ◽  
Stiffness And Damping ◽  
Diamond Probe

Reversed Micelle Structures in PFPE Lubricant Thin Films on Magnetic Disk Surface Observed by Non-Contact AFM

2008 ◽  
Vol 51 (5) ◽  
pp. 652-658 ◽  
Author(s):  
Takayuki Nakakawaji ◽  
Mina Amo ◽  
Ken-ichi Iimura ◽  
Teiji Kato ◽  
Naoyuki Torita
Keyword(s):  
Thin Films ◽  
Disk Surface ◽  
Reversed Micelle ◽  
Magnetic Disk ◽  
Pfpe Lubricant

Microstructures in Lubricant Thin Layers at the Magnetic Disk Surface, Observed Using Cryogenic Atomic Force Microscopy

2006 ◽  
Vol 59 (6) ◽  
pp. 394
Author(s):  
Teiji Kato ◽  
Takayuki Nakakawaji
Keyword(s):  
Atomic Force Microscopy ◽  
Disk Surface ◽  
Thin Layers ◽  
Solid Surfaces ◽  
Carbon Overcoat ◽  
Magnetic Disk ◽  
Force Microscopy ◽  
Atomic Force ◽  
Pfpe Lubricant ◽  
Atomically Flat

Cryogenic Atomic Force Microscopy (AFM) was used to observe perfluoropolyether (PFPE) lubricant molecules at atomically flat solid surfaces and at a magnetic disk surface to understand the lubricity of ultra-thin (1 nm) lubricant layers at the hard disk surface. Molecular imaging of PFPE lubricant molecules reveals the formation of reversed micelle structures at comparatively non-polar solid surfaces such as gold or the carbon overcoat of magnetic disks.

The Appropriate Lumped Constants of Vibrating Shaft Systems

1943 ◽  
Vol 10 (4) ◽  
pp. A220-A224
Author(s):  
G. Horvay ◽  
J. Ormondroyd
Keyword(s):  
Total Mass ◽  
Spring Constant ◽  
New Method ◽  
Concentrated Mass ◽  
Shaft System ◽  
Spring Constants

Abstract The present paper is a theoretical supplement to the descriptive article, “Static and Dynamic Spring Constants.” It is concerned with the derivation of the constants (1a)Ki=ki+16miω2=ki(1+16ϵi2)(ϵi2=ω2mi/ki)(1b)Mi=μi+12(mleft+mright) of the appropriately lumped shaft system (Section 1), and with an estimate of the range of the new method (Sections 2, 3, 4). Term ki denotes the distributed static spring constant, mi the total mass of the ith (uniform) shaft section of the system; μi is the ith concentrated mass, ω the frequency of vibration.

Stiffness and Damping Forces in the Intervertebral Joints of Blue Marlin (Makaira Nigricans)

1992 ◽  
Vol 162 (1) ◽  
pp. 131-155 ◽  
Author(s):  
JOHN H. LONG
Keyword(s):  
Regional Variation ◽  
Vertebral Column ◽  
Damping Coefficient ◽  
Complete Cycle ◽  
Blue Marlin ◽  
Makaira Nigricans ◽  
External Moment ◽  
Order Of Magnitude ◽  
Dynamic Bending ◽  
Stiffness And Damping

The stiffness and damping moments that are transmitted by intervertebral joints during sinusoidal bending were determined in the blue marlin, Makaira nigricans Lacépède. Using a dynamic bending machine, the angular stiffness (N m rad−1) and damping coefficient (kg m2 rad−2 s−1) of the intervertebral joints were measured over a range of bending frequencies, amplitudes and positions along the backbone. Angular stiffness increases with increasing bending amplitude, but, for some joints, the rate at which it changes with increasing bending frequency is negative. The precaudal intervertebral joints are less stiff than the caudal joints. The damping coefficient, which also shows regional variation, does not change with amplitude but does decrease with increasing bending frequency in joint positions three and five. Stiffness moments along the vertebral column, given the same amount of bending at each joint, are always greater than the damping moments. However, damping moments increase by an order of magnitude with an increase in bending frequency from 0.5 to 5.0Hz. The stiffness and damping moments determine the work that an external moment, such as muscle, must do over a complete cycle of bending. The external moments and work needed to bend an intervertebral joint are determined largely by the stiffness moments of the intervertebral joints.

Research on the Tension Effects on Automobile Damping Synchronous Belt Transmission System Damping and Dynamic Stiffness

2014 ◽  
Vol 687-691 ◽  
pp. 407-410
Author(s):  
Yao Chen Shi ◽  
Zhan Guo Li ◽  
Dan Liu
Keyword(s):  
Solution Method ◽  
Dynamic Stiffness ◽  
Damping Coefficient ◽  
Stiffness Coefficient ◽  
Driving System ◽  
Automotive Engine ◽  
Vibration Absorption ◽  
Belt Transmission ◽  
Stiffness And Damping ◽  
Main Factor

because of the synchronism belts driving has the advantages of vibration absorption, noise reduction, constant transmission ratio, so it is widely used in automotive engine timing driving system, The stiffness and damping coefficients of the synchronous belt is the main factor affecting the synchronous belt transmission in the process of vibration and noise. In this paper, the model W automotive synchronous belt is simplified as a spring damper system, to solve the stiffness coefficient and damping coefficient of synchronous belt, design of a device for measuring the synchronous belt stiffness coefficient and damping coefficient, measured the belt stiffness coefficient and damping coefficient in the conditions of different tension, and the accuracy of the solution method for synchronous belt stiffness coefficient and damping coefficient was verified as well.

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