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AN ALTERNATIVE SIMULATION METHOD FOR CALCULATION OF MICROGAS FLOWS UNDER FLYING HEAD SLIDERS
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Ching Shen
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The precise knowledge of the force and moment generated by the air squeezed under the read-write slider by the rotating disc is an
engineering necessity in designing the air bearing surface slider. This paper reviews methods addressing the thin gas film bearings
problem. It firstly reviews briefly the relatively well-known two methods of calculations of the microgas flows under flying head
sliders, the generalized Reynolds equation, having given a number of useful results of slider design, and the DSMC method, which
is precise and appropriate for the flow of complex configurations but is restricted to miniature (~micrometer) size sliders. The
main purpose of the paper is to introduce to the reader an alternative method, the information preservation (IP) method, for use
in simulation of the flows under air bearing surfaces. Some recent results of IP simulation of slider flows published on conference
proceedings are introduced here....
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FILM THICKNESS ANALYSIS FOR EHL CONTACTS UNDER STEADY-STATE AND TRANSIENT CONDITIONS BY AUTOMATIC DIGITAL IMAGE PROCESSING
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E Ciulli, T Draexl, K Stadler
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The knowledge of the film thickness values is very important in lubricated contacts to verify the lubrication conditions. Optical interferometry
is one of the most used methodologies for film thickness and shape determination of Elastohydrodynamic-lubricated
contacts. An image processing programme has been developed for the analysis of white light interferograms. The programme,
based on the analysis of the hue channel, has been developed in order to process big amounts of images, as often generated under
transient conditions. The measurement range is currently limited to a maximum film thickness of 0.7 µm. The programme has
been used for analysing several images recorded in tests carried out with a ball on disc contact under steady-state as well as transient
conditions for different velocities and slide-to-roll ratios. Under transient conditions, the entraining velocity is varied with a
sinusoidal law for two different frequencies. The results obtained evidenced an asymmetric reduction of the film thickness when
increasing the percentage of sliding, both for stationary and transient conditions. Under transient conditions with increasing test
frequency, film thickness loops of increasing amplitude have been found that reduce their amplitude more when the ball is running
faster than the disc. Squeeze and thermal effects can explain the results obtained....
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EXPERIMENTAL INVESTIGATION INTO THE TRACTIVE PREROLLING BEHAVIOR OF BALLS IN V-GROOVED RACKS
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Kris De Moerlooze, Farid Al-Bender
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In a rolling element system, the period of transition between motion commencement and the attainment of steady state, gross
rolling, and termed prerolling is of common concern to many engineering applications. This region is marked by hysteresis friction
behavior, with a characteristic friction-displacement curve, which is in particular relevant to motion characterization and control
issues. In a previous paper, the authors carried out a theoretical analysis of tractive prerolling, leading to a model for simulating this
phenomenon. The present paper is dedicated to the experimental investigation of tractive prerolling friction behavior, including
validation of the theoretical model. Firstly, a kinematic analysis of the rolling motion in V-grooved tracks is carried out. Secondly,
the influence of the normal load on the frictional behavior, in prerolling up to the attainment of gross rolling, is investigated on
a dedicated test setup. Finally, the newly developed theoretical model is validated by comparison with the experimental results.
Satisfactory agreement is obtained between theory and experiment....
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