Hydrodynamic Friction in Elliptical and Circular Point Contacts

1974 ◽  
Vol 16 (4) ◽  
pp. 243-249 ◽  
Author(s):  
N. Thorp ◽  
R. Gohar
Keyword(s):  
Drive Shaft ◽  
Hydrodynamic Theory ◽  
Experimental Measurements ◽  
Point Contacts ◽  
Hydrodynamic Friction ◽  
Circular Groove ◽  
Circular Point ◽  
The Asymmetry

Hydrodynamic friction in undistorted, concentrated point contacts is studied. Experimental measurements are obtained using a ball-and-plate machine, the plate being either flat, or with a circular groove. In the latter case, the ball drive-shaft is angled to vary the asymmetry of the contact. Reasonable correlation with experiment is obtained using a hydrodynamic theory which embraces the rolling, sliding and cavitation components of the total friction.

scholarly journals Transient analysis of isothermal elastohydrodynamic circular point contacts

2001 ◽  
Vol 215 (10) ◽  
pp. 1159-1173 ◽  
Author(s):  
D Jalali-Vahid ◽  
H Rahnejat ◽  
Z M Jin ◽  
D Dowson
Keyword(s):  
Transient Analysis ◽  
Point Contacts ◽  
Circular Point

Lubrication at point contacts

1961 ◽  
Vol 261 (1307) ◽  
pp. 532-550 ◽  
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Single Point ◽  
Applied Pressure ◽  
Hydrodynamic Theory ◽  
Radius Of Curvature ◽  
Point Contacts ◽  
Wide Range ◽  
Electrical Capacity ◽  
Classical Hydrodynamic

Measurements have been made of the friction, electrical resistance, and electrical capacity between rotating steel cylinders with their axes mutually at right angles. The lubricant was a plain hydrocarbon mineral oil. Nominally the surfaces come together at a single point and the apparatus is designed to ensure that this condition is maintained even if the cylinders wear. It is shown that hydrodynamic lubrication exists over a wide range of conditions. At loads of a few kilograms it persists even when the speed falls below 1 cm/s and at higher speeds (~ 100 cm/s) it is maintained even when the load becomes large enough to cause bulk plastic flow of hardened steel. Hitherto it has been considered that only boundary lubrication could occur under these extreme conditions. At very light loads classical hydrodynamic theory applies but as the load is increased a departure from classical theory occurs because the viscosity of the oil increases under the applied pressure. At heavier loads the pressures become large enough to cause appreciable elastic deformation of the surfaces and a state of elasto-hydrodynamic lubrication is achieved. Under elasto-hydrodynamic conditions the film thickness can be deduced from the measure­ments of electrical capacity. A simplified theory of elasto-hydrodynamic lubrication at point contacts is developed, and the measured values of film thickness are in fairly good agreement with those derived from the theory. However, the variations of film thick­ness with viscosity, speed and radius of curvature forecast by the theory differ significantly from those obtained experimentally. The values of the film thickness range from 2 x 10 -6 cm to more than 1 x 10 -4 cm. The results, over the whole range, conform to a regular pattern and there is no evidence of any disturbing influence of the surface molecular fields, even with the thinnest films.

Lubrication at Elliptical Contacts

1968 ◽  
Vol 183 (16) ◽  
pp. 138-146
Author(s):  
R. W. Snidle ◽  
J. F. Archard
Keyword(s):  
Film Thickness ◽  
Pressure Coefficient ◽  
Gear Ratio ◽  
Hydrodynamic Theory ◽  
Point Contacts ◽  
Reduced Pressure ◽  
Contact Conditions ◽  
General Validity ◽  
Hypoid Gears ◽  
Coefficient Of Viscosity

The classical hydrodynamic theory for point contacts is extended to cover the general case where the resolved hydrodynamic velocity is not directed along either of the axes of the ellipse of contact. Isobar plots of deduced values of the non-dimensional reduced pressure, q, are shown for some of these cases. A first approximation to an elastohydrodynamic film thickness equation is derived, for this general case, by equating the maximum reduced pressure generated between undeformed bodies to the inverse of the pressure coefficient of viscosity, α. The theory is applicable to the contact conditions that exist between the teeth of hypoid gears, and the variation of lubricant film thickness with pinion offset and gear ratio for a range of hypoid gear sets has been deduced. Experiments have been performed on a crossed cylinders machine, the results of which demonstrate the general validity of the theory.

scholarly journals Transient analysis of isothermal elastohydrodynamic circular point contacts

2001 ◽  
Vol 215 (10) ◽  
pp. 1159-1172 ◽  
Author(s):  
D Jalali Vahid ◽  
H Rahnejat ◽  
Z M Jin ◽  
D Downson
Keyword(s):  
Transient Analysis ◽  
Solution Method ◽  
Numerical Solutions ◽  
Flat Glass ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Good Qualitative Agreement ◽  
Circular Point ◽  
Good Agreement

In this paper a solution method is presented for the transient isothermal elastohydrodynamic lubrication of point contact conjunctions, based upon the Newton-Raphson scheme and low iteration relaxation. The numerical results are compared with the numerical and experimental observations of others for the circular point contact of a ball against a flat glass disc under oscillating conditions. Good agreement has been found with other numerical solutions. The comparison with the experimental results shows good qualitative agreement.

An Isoviscous Model for the Hydrodynamic Lubrication of Plane Strain Forging Processes With Flat Dies

1974 ◽  
Vol 96 (4) ◽  
pp. 539-546 ◽  
Author(s):  
W. R. D. Wilson
Keyword(s):  
Plane Strain ◽  
Hydrodynamic Lubrication ◽  
Hydrodynamic Theory ◽  
Experimental Measurements ◽  
Maximum Thickness ◽  
Good Agreement

Transient isoviscous hydrodynamic theory is used to investigate the lubrication of plane strain forging processes with flat dies. It is shown that during yielding a film which decreases from a maximum thickness at the center of the contact to zero at the edges is formed. As the deformation continues, the film is transported outwards at half the surface speed of the workpiece. In the case where the dies extend beyond the workpiece, an unlubricated region is formed. The variation in width of this region with reduction predicted by the model is in good agreement with experimental measurements.

Isoviscous elastohydrodynamic lubrication of circular point contacts with particular reference to metal-on-metal hip implants

2003 ◽  
Vol 217 (5) ◽  
pp. 397-402 ◽  
Author(s):  
D Jalali- Vahid ◽  
Z. M. Jin ◽  
D Dowson
Keyword(s):  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Hip Implants ◽  
Point Contacts ◽  
Hip Joints ◽  
Circular Point ◽  
Metal On Metal ◽  
Artificial Hip Joints

A full numerical analysis of elastohydrodynamic lubrication (EHL) of circular point contacts was carried out in the present study under isoviscous conditions with particular reference to metal-on-metal artificial hip joints, using a modified Newton-Raphson method. It was found to be possible to incorporate directly the physiological conditions, representative of typical metal-on-metal hip implants under in-vivo walking or in-vitro simulator testing, in the present numerical solutions. The predicted minimum and central film thicknesses were compared favourably with those estimated from various formulae available in the literature. In particular, it was shown that both the minimum and the central film thickness expressions derived by Hamrock and Dowson were reasonably accurate for all the conditions considered in the present study.

scholarly journals Boundary Conditions for Elastohydrodynamics of Circular Point Contacts

2013 ◽  
Vol 53 (1) ◽  
pp. 107-118 ◽  
Author(s):  
M. Mohammadpour ◽  
P. M. Johns-Rahnejat ◽  
H. Rahnejat ◽  
R. Gohar
Keyword(s):  
Boundary Conditions ◽  
Point Contacts ◽  
Circular Point
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