Hydrodynamic Lubrication of Hydrostatic Extrusion

1976 ◽  
Vol 98 (1) ◽  
pp. 27-31 ◽  
Author(s):  
W. R. D. Wilson ◽  
S. M. Mahdavian
Keyword(s):  
Film Thickness ◽  
Castor Oil ◽  
Hydrodynamic Lubrication ◽  
Film Formation ◽  
Hydrostatic Extrusion ◽  
Work Zone ◽  
Thickness Variation ◽  
Viscous Heating ◽  
Theoretical Predictions ◽  
Good Agreement

An analytical model for the hydrodynamic lubrication of hydrostatic extrusion is developed. This includes the effect of viscous heating on the film formation process and the effect of viscous and plastic heating on the friction and film thickness variation in the work zone. Theoretical predictions of film thickness and extrusion pressure show good agreement with experimental measurements for aluminum billets lubricated with castor oil.

A Refined Analytical Model for Hydrodynamic Lubrication of Cold Extrusion and Its Comparison With Experiment

1982 ◽  
Vol 104 (1) ◽  
pp. 46-52 ◽  
Author(s):  
S. M. Mahdavian
Keyword(s):  
Analytical Model ◽  
Castor Oil ◽  
Hydrodynamic Lubrication ◽  
Work Zone ◽  
Extrusion Pressure ◽  
Cold Extrusion ◽  
Viscous Heating ◽  
Theoretical Estimation ◽  
Comparison With Experiment ◽  
Inlet Zone

In a refined analytical model for the hydrodynamic lubrication of cold extrusion, effects of viscous heating in the inlet zone and surface temperature in the work zone are included to estimate extrusion pressure for both unsteady and steady lubrication. An experimental study indicates that a hydrodynamic lubricant film may be formed by reducing friction at the start of extrusion by a secondary lubricant. Theoretical estimation of unsteady extrusion pressure is in agreement for extrusion of aluminium billets lubricated with castor oil.

Hydrofilm Extrusion of Tubes Through Optimized Curved Dies

1983 ◽  
Vol 105 (4) ◽  
pp. 243-250 ◽  
Author(s):  
N. S. Cho ◽  
D. Y. Yang
Keyword(s):  
Energy Minimization ◽  
Castor Oil ◽  
Room Temperature ◽  
Hydrodynamic Lubrication ◽  
Film Formation ◽  
Fluid Viscosity ◽  
Pressure Distributions ◽  
Die Profile ◽  
Hydrodynamic Lubrication Theory ◽  
Good Agreement

An analytical method for hydrofilm extrusion of axisymmetric tubes through optimized curved dies is proposed. The upper-bound method and hydrodynamic lubrication theory are used in combination. The work-hardening effect of metal and the variation of fluid viscosity are taken into consideration. The optimal film thickness and the optimal die profile are found through energy minimization, and also pressure distributions of the fluid are obtained. A new mandrel system is devised for the film formation at the mandrel-billet interface. Experiments were carried out at room temperature for various diameter ratios of the tube, using the axisymmetric curved die. The theoretical prediction of extrusion pressure shows good agreement with experimental measurements for mild steel specimens, using castor oil as the lubricant.

Some Limitations in Applying Classical EHD Film Thickness Formulas to a High-Speed Bearing

1981 ◽  
Vol 103 (2) ◽  
pp. 295-301 ◽  
Author(s):  
J. J. Coy ◽  
E. V. Zaretsky
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Heating Effects ◽  
Theoretical Predictions ◽  
Traction Fluid ◽  
Shear Heating ◽  
Thickness Measurements ◽  
Inner Race ◽  
Maximum Stresses ◽  
Good Agreement

Elastohydrodynamic film thickness was measured for a 20-mm ball bearing using the capacitance technique. The bearing was thrust loaded to 90, 448, and 778 N (20, 100, and 175 lb). The corresponding maximum stresses on the inner race were 1.28, 2.09, and 2.45 GPa (185,000, 303,000, and 356,000 psi). Test speeds ranged from 400 to 14,000 rpm. Film thickness measurements were taken with four different lubricants: (a) synthetic paraffinic, (b) synthetic paraffinic with additives, (c) neopentylpolyol (tetra) ester meeting MIL-L-23699A specifications, and (d) synthetic cycloaliphatic hydrocarbon traction fluid. The test bearing was mist lubricated. Test temperatures were 300, 338, and 393 K. The measured results were compared to theoretical predictions using the formulae of Grubin, Archard and Cowking, Dowson and Higginson, and Hamrock and Dowson. There was good agreement with theory at low dimensionless speed, but the film was much smaller than theory predicts at higher speeds. This was due to kinematic starvation and inlet shear heating effects. Comparisons with Chiu’s theory on starvation and Cheng’s theory on inlet shear heating were made.

An Experimental Investigation of Lubrication in Hydrostatic Extrusion Using Wax as a Model Material

1972 ◽  
Vol 94 (3) ◽  
pp. 913-919 ◽  
Author(s):  
A. Wuerscher ◽  
W. B. Rice
Keyword(s):  
Thin Film ◽  
Castor Oil ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Pressure Fluctuations ◽  
Model Material ◽  
Hydrostatic Extrusion ◽  
Strain Rates ◽  
The Coefficient Of Friction ◽  
Bearing Friction

This paper describes hydrostatic extrusion experiments in which paraffin wax was extruded, undertaken to test the validity of a theory proposed by Iyengar and Rice concerning the conditions necessary for hydrodynamic lubrication. Three fluids were used: castor oil, and two silicone fluids. Stress-strain curves obtained at several strain rates revealed that the particular wax behaves like many metals in that Y = Aεm. Strain-rates in the die are assessed, and corresponding values of Y are incorporated in the Hoffman and Sachs analysis of extrusion, which is then used to estimate the coefficient of friction from observed values of extrusion pressure. Analogy with journal bearing friction phenomena leads to the conclusion that at higher speeds hydrodynamic lubrication was attained with all three fluids, but that it was “thin-film” rather than “thick-film” predicted for similar billet speeds. Violent pressure fluctuations observed at higher speeds with castor oil, but not with the silicone fluids are attributed to smaller compressibility and viscosity of the castor oil.

Hydrodynamic Lubrication in Axisymmetric Stretch Forming—Part 2: Experimental Investigation

1991 ◽  
Vol 113 (4) ◽  
pp. 667-674 ◽  
Author(s):  
L. G. Hector ◽  
W. R. D. Wilson
Keyword(s):  
Experimental Investigation ◽  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Lubricant Film ◽  
Lubricant Film Thickness ◽  
Stretch Forming ◽  
Workpiece Material ◽  
Contour Map ◽  
Theoretical Predictions ◽  
Interference Studies

In order to test the validity of the theoretical model discussed in Part 1, an experimental technique, employing optical interferometry, has been developed to measure lubricant film thickness during axisymmetric stretch forming. Specially fabricated, transparent punches are used for both double and multiple beam interference studies. The choice of workpiece material, lubricant, and forming speed ensures that the punch/sheet conjunction will be hydrodynamically lubricated during most of the process. Interference patterns, due to the variable film of lubricant separating the punch and sheet surfaces, are formed as the sheet wraps around the punch. These patterns provide a contour map of the lubricant film thickness along the punch/sheet conjunction. The measured film thickness, as taken from an interpretation of the patterns, is compared with the theoretical predictions of Part 1.

Isoviscous Hydrodynamic Lubrication of Deep Drawing and Its Comparison With Experiment

1993 ◽  
Vol 115 (1) ◽  
pp. 111-118 ◽  
Author(s):  
S. M. Mahdavian ◽  
Z. M. Shao
Keyword(s):  
Film Thickness ◽  
Deep Drawing ◽  
Hydrodynamic Lubrication ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Blank Holder ◽  
Comparison With Experiment ◽  
Force Ratio ◽  
Theoretical Predictions ◽  
Metal Blank

An analytical model for the isoviscous hydrodynamic lubrication of deep drawing is developed. The model covers the complete drawing stages from sheet metal blank to the drawn cup-shaped product. Equations to calculate the film thickness, radial, and drawing stresses related to the blank holder squeezing action are presented. Theoretical predictions of both film thickness and drawing force ratio for lubricated, low carbon steel are compared with experimental measurements.

The Effect of Kinematic Conditions on Film Thickness in Compliant Lubricated Contact

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
David Nečas ◽  
Tomáš Jaroš ◽  
Kryštof Dočkal ◽  
Petr Šperka ◽  
Martin Vrbka ◽  
...  
Keyword(s):  
Film Thickness ◽  
Optical Glass ◽  
Film Formation ◽  
Fluorescent Microscopy ◽  
Elastohydrodynamic Lubrication ◽  
Constant Load ◽  
Fluid Viscosity ◽  
Lubricating Film ◽  
Theoretical Predictions ◽  
Lubricated Contact

The present paper deals with an investigation of film formation in compliant lubricated contact. Despite these contacts can be found in many applications of daily life including both biological and technical fields, so far little is known about the lubrication mechanisms inside the contacts. The main attention is paid to the effect of kinematic conditions on central film thickness. For this purpose, fluorescent microscopy method was employed. Experiments were realized in ball-on-disk configuration, while the ball was made from rubber and the disk was from optical glass. The contact was lubricated by glycerol and polyglycol to examine the effect of fluid viscosity. The measurements were conducted under pure rolling and rolling/sliding conditions. The entrainment speed varied from 10 to 400 mm/s and constant load of 0.2 N was applied. Experimental results were compared with two theoretical predictions derived for isoviscous-elastohydrodynamic lubrication (I-EHL) regime. It was found that the thickness of lubricating film gradually increases with increasing entrainment speed, which corresponds to theoretical assumptions. Against expectations, evident influence of slide-to-roll ratio (SRR) on film formation was observed. In the last part of the paper, some limitations of this study are discussed and several recommendations for further methodology improvement are suggested.

Isothermal Hydrodynamic Lubrication in Hydrostatic Extrusion of a Work-Hardening Material

1979 ◽  
Vol 101 (3) ◽  
pp. 386-389 ◽  
Author(s):  
S. Thiruvarudchelvan
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Numerical Method ◽  
Work Hardening ◽  
Critical Speed ◽  
Hydrodynamic Lubrication ◽  
Hydrostatic Extrusion ◽  
Extrusion Pressure ◽  
Hydrodynamic Conditions ◽  
Hardening Material

Using a numerical method the film thickness and the pressure distribution in hydrostatic extrusion of a work-hardening material under hydrodynamic conditions are determined. A minimum or critical speed for full fluid lubrication to develop is predicted. The effect of the length of die-land on the critical speed, and the effect of speeds above the critical speed on the extrusion pressure are also presented.

Refined Models for Hydrodynamic Lubrication in Axisymmetric Stretch Forming

1994 ◽  
Vol 116 (1) ◽  
pp. 101-109 ◽  
Author(s):  
Tze-Chi Hsu ◽  
William R. D. Wilson
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
The Other ◽  
Lubricant Film Thickness ◽  
Stretch Forming ◽  
Sheet Bending ◽  
Membrane Stiffness ◽  
Thickness Measurements ◽  
Sheet Deformation ◽  
Good Agreement

Two mathematical models for axisymmetric stretch forming with a spherical punch are developed. The models combine a finite element representation of the sheet deformation with a hydrodynamic lubrication model. In one model the influence of sheet bending stiffness is taken into account while in the other only the membrane stiffness is considered. Comparison of the predictions of the models with the film thickness measurements of Hector and Wilson indicates that the inclusion of elastic effects is important in predicting lubricant film thickness. The results of the bending model are in particularly good agreement with the experimental data. A useful analytical method for predicting the film thickness at the center of the conjunction at the onset of yield is also developed.

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