On the Lubrication of Rough Rollers

1984 ◽  
Vol 106 (2) ◽  
pp. 211-217 ◽  
Author(s):  
J. Prakash
Keyword(s):  
Surface Roughness ◽  
Stochastic Model ◽  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Roughness Parameter ◽  
Dimensionless Parameters ◽  
Surface Roughness Parameter ◽  
Cylinder Radius ◽  
Minimum Film Thickness ◽  
Effect Of Surface

Christensen’s stochastic model of hydrodynamic lubrication as extended to two sided roughness is used to study the effect of surface roughness in the analysis of lightly loaded rollers in combined rolling, sliding and normal motion. A detailed study of the above system in terms of dimensionless parameters, Q (involving the normal and entraining velocity, the minimum film thickness and the equivalent cylinder radius); the slide roll ratio and the surface roughness parameter is made for purely longitudinal and purely transverse surface roughness.

Rough Soft-EHL with Non-Newtonian Lubricant

2015 ◽  
Vol 736 ◽  
pp. 57-63
Author(s):  
Panichakorn Jesda ◽  
Wongseedakeaw Khanittha
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Film Thickness ◽  
Modulus Of Elasticity ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Film Pressure ◽  
Coefficient Increase ◽  
Minimum Film Thickness ◽  
Effect Of Surface

This paper presents the effect of surface roughness on soft elastohydrodynamic lubrication in circular contact with non-Newtonian lubricant. The time independent modified Reynolds equation, elastic equation and lubricant viscosity equation were formulated for compressible fluid. Perturbation method, Newton-Raphson method, finite different method and full adaptive multigrid method were implemented to obtain the film pressure, film thickness profiles and friction coefficient in the contact region at various the amplitude of surface roughness, surface speed of sphere, modulus of elasticity and radius of sphere. The simulation results showed that the film thickness in contact region depended on the profile of surface roughness. The minimum film thickness decreased but maximum film pressure and friction coefficient increase when the amplitude of surface roughness and modulus of elasticity increased. For increasing surface speeds, the minimum film thickness and friction coefficient increase but maximum film pressure decreases. When radius of sphere increases, the minimum film thickness increases but maximum film pressure and friction coefficient decrease.

The Effect of Surface Roughness on the Average Film Thickness Between Lubricated Rollers

1976 ◽  
Vol 98 (1) ◽  
pp. 117-124 ◽  
Author(s):  
L. S. H. Chow ◽  
H. S. Cheng
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Stochastic Models ◽  
Hydrodynamic Lubrication ◽  
Elastohydrodynamic Lubrication ◽  
Type Equation ◽  
Slider Bearing ◽  
Reduced Pressure ◽  
Average Film Thickness ◽  
Effect Of Surface

The Christensen theory of stochastic models [7] for hydrodynamic lubrication of rough surfaces is extended to elastohydrodynamic lubrication between two rollers. The Grubin-type equation including asperity effects in the inlet region is derived. Solutions for the reduced pressure at the entrance as a function of the ratio of the average nominal film thickness to the r.m.s. surface roughness (in terms of standard deviation σ), have been obtained numerically. Results were obtained for purely transverse as well as purely longitudinal surface roughness for cases with or without slip. The reduced pressure is shown to decrease slightly by considering longitudinal surface roughness. The transverse surface roughness, on the other hand, has a slight beneficial effect on the average film thickess at the inlet. The same approach was used to study the effect of surface roughness on lubrication between rigid rollers and lubrication of an infinitely-wide slider bearing. Results of these two cases show that the effects of surface roughness are similar to those found in elastohydrodynamic contacts.

Effects of Surface Roughness on Elastohydrodynamic Lubrication in Elliptical Contact with Non-Newtonian Fluids

2012 ◽  
Vol 482-484 ◽  
pp. 1057-1061
Author(s):  
Sountaree Rattapasakorn ◽  
Jesda Panichakorn ◽  
Mongkol Mongkolwongrojn
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Film Thickness ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Film Pressure ◽  
Minimum Film Thickness ◽  
Roughness Amplitude ◽  
Elliptical Contact ◽  
Effect Of Surface

This paper presents the effect of surface roughness on the performance characteristics of elastohydrodynamic lubrication with non-Newtonian fluid base on Carreau viscosity model in elliptical contact. The time independent modified Reynolds equation and elastic equation were formulated for compressible fluid. Perturbation method, Newton Raphson method and full adaptive multigrid method were implemented to obtain the film pressure, film thickness profiles and friction coefficient in the contact region at various amplitude of combined surface roughness, applied loads, speeds and elliptic ratio. Simulation results show surface roughness amplitude has significant affected the film pressure in the contact region. The minimum film thickness decreases but friction coefficient increases when the combined roughness and applied loads increases. The minimum film thickness and friction coefficient both increase as the relative velocity of the ball and the plate is increase. For increasing the elliptic ratio, the minimum film thickness increases but the friction coefficient decreases.

Surface Roughness at Wire Electrical Discharge Machining

2015 ◽  
Vol 760 ◽  
pp. 551-556 ◽  
Author(s):  
Oana Dodun ◽  
Laurenţiu Slătineanu ◽  
Margareta Coteaţă ◽  
Vasile Merticaru ◽  
Gheorghe Nagîţ
Keyword(s):  
Surface Roughness ◽  
Empirical Model ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Roughness Parameter ◽  
Wire Electrical Discharge Machining ◽  
Power Type ◽  
Surface Roughness Parameter ◽  
Pulse On Time ◽  
Pulse Off Time

Wire electrical discharge machining is a machining method by which parts having various contours could be detached from plate workpieces. The method uses the electrical discharges developed between the workpiece and the wire tool electrode found in an axial motion, when in the work zone a dielectric fluid is recirculated. In order to highlight the influence exerted by some input process factors on the surface roughness parameter Ra in case of a workpiece made of an alloyed steel, a factorial experiment with six independent variables at two variation levels was designed and materialized. As input factors, one used the workpiece thickness, pulse on time, pulse off-time, wire axial tensile force, current intensity average amplitude defined by setting button position and travelling wire electrode speed. By mathematical processing of the experimental results, empirical models were established. Om the base of a power type empirical model, graphical representations aiming to highlight the influence of some input factors on the surface roughness parameter Ra were achieved. The power type empirical model facilitated establishing of order of factors able to exert influence on the surface roughness parameter Ra at wire electrical discharge machining.

scholarly journals Coastal Boundary Layer Characteristics of Wind, Turbulence, and Surface Roughness Parameter over the Thumba Equatorial Rocket Launching Station, India

2014 ◽  
Vol 2014 ◽  
pp. 1-21 ◽  
Author(s):  
K. V. S. Namboodiri ◽  
Dileep Puthillam Krishnan ◽  
Rahul Karunakaran Nileshwar ◽  
Koshy Mammen ◽  
Nadimpally Kiran kumar
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Wind Direction ◽  
Roughness Parameter ◽  
Turbulent Heat ◽  
Surface Roughness Parameter ◽  
South West Monsoon ◽  
Wind Turbulence ◽  
Coastal Boundary Layer ◽  
Coastal Boundary

The study discusses the features of wind, turbulence, and surface roughness parameter over the coastal boundary layer of the Peninsular Indian Station, Thumba Equatorial Rocket Launching Station (TERLS). Every 5 min measurements from an ultrasonic anemometer at 3.3 m agl from May 2007 to December 2012 are used for this work. Symmetries in mesoscale turbulence, stress off-wind angle computations, structure of scalar wind, resultant wind direction, momentum flux (M), Obukhov length (L), frictional velocity (u*), w-component, turbulent heat flux (H), drag coefficient (CD), turbulent intensities, standard deviation of wind directions (σθ), wind steadiness factor-σθ relationship, bivariate normal distribution (BND) wind model, surface roughness parameter (z0), z0 and wind direction (θ) relationship, and variation of z0 with the Indian South West monsoon activity are discussed.

Considerations Regarding Some Surface State Parameters Characterized by a more Restricted Use

2015 ◽  
Vol 809-810 ◽  
pp. 93-98
Author(s):  
Ionuţ Urzică ◽  
Ciprian Râznic ◽  
Mihai Apostol ◽  
Corina Mihaela Pavăl ◽  
Mihai Boca ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Roughness Parameter ◽  
Cutting Speed ◽  
Roughness Parameters ◽  
Turning Process ◽  
Nose Radius ◽  
Machined Surface ◽  
Surface Roughness Parameter ◽  
Surface Roughness Parameters ◽  
Restricted Use

Frequently, on the drawings of mechanical parts, only indications concerning the surface roughness parameter Ra and, relatively rarely, the surface roughness parameter Rz are included. However, the study of the machined surface roughness highlights the necessity to use yet other surface roughness parameters, in order to have a clearer image on the state of the machined surface. Some other surface roughness parameters possible to be used and presenting importance, without the parameters Ra and Rz, were highlighted. One took into consideration the possibility of measuring parameters Rsk and Rmr by means of the available surface roughness testers. Experimental researches of turning by applying the method of full factorial experiment were developed. As input factors in turning process, the cutting speed, the feed rate and the tool nose radius were used. The experimental results were mathematically processed, being determined empirical mathematical models that highlight the influence of certain input factors of turning process on the values of some surface roughness parameters characterized by a more restricted use

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