The Causes of Asymmetric Deformation of Surface Roughness Asperities in EHL Contacts

2021 ◽  
pp. 1-38
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Hiroshi Nishikawa
Keyword(s):  
Thermal Conductivity ◽  
Surface Roughness ◽  
Contact Pressure ◽  
Elastic Moduli ◽  
Elastohydrodynamic Lubrication ◽  
The Other ◽  
Contact Materials ◽  
Oil Film ◽  
Asymmetric Deformation ◽  
The Difference

Abstract This paper provides the main causes of asymmetric or directional deformation of surface roughness based on a transient non-Newtonian thermal elastohydrodynamic lubrication (EHL) model, where the contact materials have different thermal conductivities and elastic moduli. It is clarified that the asymmetric deformation of the asperities appears due to two causes. One depends on the slide-roll ratio and the difference in thermal conductivity between contact materials, and the other is caused by the contact pressure between the asperities through the oil film.

Effects of Thermal Properties of Contact Materials and Slide-Roll Ratio in Elastohydrodynamic Lubrication

2021 ◽  
pp. 1-34
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Hiroshi Nishikawa
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Film Thickness ◽  
Thermal Inertia ◽  
Elastohydrodynamic Lubrication ◽  
Mechanical And Thermal Properties ◽  
Contact Materials ◽  
The Difference ◽  
Thermal Ehl

Abstract The effects of thermal conductivity, heat capacity, thermal inertia and slide-roll ratio on point elastohydrodynamic lubrication (EHL) are discussed with engineering ceramics and steel by a non-Newtonian thermal EHL analysis. When the thermal conductivities of contacting materials are significantly different, the film thickness is greatly affected by which material has the higher velocity. However, the film thickness is dominated by the heat capacity when the difference in thermal conductivity is not large. In contact of materials with the same mechanical and thermal properties, the central film thickness and friction coefficient are influenced by the thermal inertia.

Cross-Property Relations between Elastic and Thermal Properties of Porous Ceramics

2006 ◽  
Vol 45 ◽  
pp. 107-112 ◽  
Author(s):  
W. Pabst ◽  
Eva Gregorová
Keyword(s):  
Thermal Conductivity ◽  
Elastic Moduli ◽  
Porous Alumina ◽  
Tensile Modulus ◽  
Porous Ceramics ◽  
The Other ◽  
Composite Ceramics ◽  
Shear Moduli ◽  
Property Relations ◽  
The One

The cross-property relations between the elastic moduli and the thermal conductivity of porous ceramics are reviewed from the viewpoint of micromechanics (composite theory). Consequences of the rigorous Milton-Torquato and Gibiansky-Torquato relations (in the form of bounds, i.e. inequalities derived between bulk or shear moduli on the one hand and thermal conductivity on the other) are compared to various approximate relations (equalities) recently proposed between the tensile modulus (Young’s modulus) and thermal conductivity, among them the two new cross-property relations proposed by the authors. The relations are critically discussed and applied to the case of porous alumina, zirconia and alumina-zirconia composite ceramics.

Effects of Elastic Moduli of Contact Surfaces in Elastohydrodynamic Lubrication

1992 ◽  
Vol 114 (1) ◽  
pp. 75-80 ◽  
Author(s):  
M. Kaneta ◽  
H. Nishikawa ◽  
K. Kameishi ◽  
T. Sakai ◽  
N. Ohno
Keyword(s):  
Elastic Moduli ◽  
Elastohydrodynamic Lubrication ◽  
Tangent Plane ◽  
Squeeze Film ◽  
Entrainment Velocity ◽  
Squeeze Film Effect ◽  
Contact Surfaces ◽  
The Difference ◽  
Surface Deflections ◽  
Film Profile

Using the optical interferometry technique the film profile in circular elastohydrodynamic contacts is examined with several kinds of fluid under wide ranges of loads and speeds. It is found that under a sliding condition a deep conical depression (dimple) occurs in the contact surface in place of the flat plateau predicted by the EHL theory. This dimple phenomena can be explained by the squeeze film effect acting parallel to the contact plane attributable to the difference in surface deflections of the contact bodies. That is, if the contacting bodies are different in their elastic moduli, EHL film shape is markedly influenced by the slide/roll ratio even if the rolling or entrainment velocity is kept constant. This result suggests that the establishment of a new EHL theory, which takes into consideration the effects of the difference in elastic moduli of the contacting surfaces and surface pressure components parallel to the contact tangent plane, is necessary for deeper understanding of the EHL regime.

Elastohydrodynamic Lubrication Between Rolling and Sliding Ceramic Cylinders: An Experimental Investigation1

2000 ◽  
Vol 122 (4) ◽  
pp. 721-724 ◽  
Author(s):  
T. Sperrfechter ◽  
R. Haller
Keyword(s):  
Thermal Conductivity ◽  
Film Thickness ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Elastohydrodynamic Lubrication ◽  
Ceramic Materials ◽  
Oil Film ◽  
Thin Film Sensors ◽  
Line Contacts ◽  
Clear Increase

The present work focuses on the investigation of the influence of bulk ceramic materials on the behavior of elastohydrodynamically (EHD) lubricated line contacts. The materials alumina Al2O3, zirconium oxide ZrO2 and aluminum nitride (AIN) are used. Comparative measurements were taken with steel disks made of 42CrMo4. Of primary importance are the material parameters Young’s modulus and thermal conductivity. The experimental variables pressure, temperature and oil film thickness in the EHD contact of a two disk test rig were measured with the aid of evaporated thin film sensors. As the results show, an increase in the Young’s modulus causes a clear increase of the pressure level. The oil film thickness distributions show a decline of the flattening width and of the constriction occurring at the contact outlet. The influence of the material with respect to its thermal conductivity dominates, above all, in the region of the load transmitting contact zone. The transition from a good to a bad conductor of heat causes a rise in temperature, more prominent for materials with lower thermal conductivities. This leads to viscosity decrease causing clearly reduced oil film thicknesses in the contact. [S0742-4787(00)01404-1]

Effects of the thermal conductivity of contact materials on elastohydrodynamic lubrication characteristics

2010 ◽  
Vol 224 (12) ◽  
pp. 2577-2587 ◽  
Author(s):  
M Kaneta ◽  
P Yang
Keyword(s):  
Thermal Conductivity ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Fluid Film ◽  
Contact Materials ◽  
Entrainment Velocity ◽  
Pressure Distributions ◽  
Traction Coefficient ◽  
Lubrication Characteristics ◽  
Lubricant Viscosity

Isothermal elastohydrodynamic lubrication (EHL) theory has brought the improvement in function, performance, and durability of machine elements with concentrated contacts. The main reason is that the theory can evaluate the lubrication characteristics, such as film thickness and pressure distributions, from the shape and size of contacting materials, lubricant viscosity at the entrance to the EHL conjunction, entrainment velocity, equivalent elastic modulus, and applied load. However, in order to estimate the film thickness and pressure distributions more accurately and to make clear the traction behaviour based on lubricant rheology, it is necessary to establish thermal EHL theory, which incorporates heat generation in the fluid film and heat transfer in the machine system on the foundation of isothermal EHL theory. The thermal conductivity of contact materials controls temperature in the fluid film and consequently the lubricant viscosity. Therefore, the EHL characteristics are affected remarkably by the thermal conductivity of contact materials. In this article, the effects of the thermal conductivity of contacting materials on the film thickness, pressure, and traction coefficient are described.

EUTECTIC SOLIDIFICATION IN METALS

1951 ◽  
Vol 29 (4) ◽  
pp. 320-327 ◽  
Author(s):  
W. C. Winegard ◽  
S. Majka ◽  
B. M. Thall ◽  
B. Chalmers
Keyword(s):  
Thermal Conductivity ◽  
Eutectic Structure ◽  
The Other ◽  
Eutectic Solidification ◽  
The Difference ◽  
Two Phases

A study has been made of the process of solidification of the alloys of tin and lead the eutectic structure of which is typically lamellar. A technique was developed in which the rate and direction of solidification were controlled. It was demonstrated that freezing takes place by the simultaneous edgewise growth of the lamellae, the thickness of which depends on the rate of freezing. It was also shown that the interface between solid and liquid at any instant is corrugated, owing to the fact that one of the phases is in advance of the other. This is attributed to the difference in thermal conductivity of the two phases. A detailed description is given of the process of eutectic solidification

scholarly journals EHL oil film thickness under rolling-sliding contact

1970 ◽  
Vol 38 ◽  
pp. 58-60 ◽  
Author(s):  
DM Nuruzzaman ◽  
MAA Sheikh
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Mechanical Engineering ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Speed ◽  
Sliding Contact ◽  
Slip Ratio ◽  
Oil Film

The Elastohydrodynamic lubrication (EHL) minimum oil film thickness is theoretically investigated under rolling with sliding contact. The effects of contact pressure, rolling speed and slip ratio on the EHL minimum oil film thickness are calculated numerically. It is found that for a range of contact pressure from 0.5 to 3.5 GPa, the minimum oil film thickness gradually decreases with the increase in contact pressure. As the rolling speed increases from 3500 to 4500 rpm, oil film thickness is increased. It is also found that the oil film thickness is not much influenced by the slip ratio. Keywords: EHL oil film thickness, Contact pressure, Rolling speed, Slip ratio. DOI: 10.3329/jme.v38i0.902 Journal of Mechanical Engineering Vol.38 Dec. 2007 pp.58-60

Gears: Elastohydrodynamic lubrication and durability

2000 ◽  
Vol 214 (1) ◽  
pp. 39-50 ◽  
Author(s):  
R. W. Snidle ◽  
H. P. Evans ◽  
M. P. Alanou
Keyword(s):  
Thin Film ◽  
Surface Roughness ◽  
Gear Tooth ◽  
Elastohydrodynamic Lubrication ◽  
Lubrication Theory ◽  
Lubricating Oil ◽  
Oil Film ◽  
Recent Developments ◽  
Surface Durability ◽  
Surface Distress

The paper presents a brief review of developments in understanding of gear tooth contact lubrication in relation to problems of surface durability and distress. Gear tooth contacts tend to operate under conditions where the lubricating oil film is thin compared with surface roughness. This feature is shown to have a significant effect on scuffing capacity and friction and is also thought to be a factor in micropitting. Recent developments in thin-film micro-elastohydrodynamic lubrication theory are described and these should lead to a better understanding of the behaviour and modes of surface distress in gears. The paper also describes the application of elastohydrodynamic analysis to other transmission components such as high-conformity gears and thrust cones.

Numerical Study on Effect of Thermal Conductivity in Point Contacts With Longitudinal Roughness on Abnormal Pressure Distribution

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Jing Wang ◽  
Peiran Yang
Keyword(s):  
Thermal Conductivity ◽  
Numerical Study ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Variation ◽  
Point Contacts ◽  
Contact Materials ◽  
Opposite Case ◽  
Abnormal Pressure ◽  
Longitudinal Roughness

Abstract In order to clarify the effect of thermal conductivity on non-Newtonian thermal elastohydrodynamic lubrication (EHL) in the point contact with longitudinal roughness on one surface or on both surfaces, numerical calculations are carried out. The contact is formed by ceramics and steel. The surface shapes of both contact solids are investigated separately. It was found that the pressure at ridges shows lower than that at grooves when the speed of a material with low thermal conductivity is faster than that of a material with high thermal conductivity. In the opposite case, such a phenomenon never occurs. This abnormal pressure variation is largely affected by the combination of contact materials and running conditions.

Numerical Study on the Interaction of Transverse and Longitudinal Roughness on Elastohydrodynamic Lubrication Contact Surfaces With Different Thermal Conductivities and Elastic Moduli

2020 ◽  
Vol 143 (9) ◽  
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Jing Wang ◽  
Jinlei Cui ◽  
Peiran Yang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Finite Length ◽  
Elastic Moduli ◽  
Elastohydrodynamic Lubrication ◽  
High Thermal Conductivity ◽  
Low Thermal Conductivity ◽  
Longitudinal Roughness ◽  
Transverse Roughness ◽  
Contact Surfaces ◽  
Thermal Conductivities

Abstract The interaction and surface features between point contact surfaces composed of longitudinal roughness with infinite or finite length and transverse roughness were discussed based on a transient non-Newtonian thermal elastohydrodynamic lubrication (EHL) model. Each surface shape is greatly affected by the difference in elastic moduli, thermal conductivities, and velocities of both contact surfaces. There is a large difference in pressure behavior when the transverse roughness is in contact with the longitudinal roughness with finite length and when it is in contact with the longitudinal roughness with infinite length. In the contact between surfaces with infinitely long longitudinal and transverse roughness, the friction coefficient is lower when the surface with longitudinal roughness has a low thermal conductivity than when it has a high thermal conductivity. Furthermore, the pressure fluctuation is larger when the transverse roughness surface has a high thermal conductivity than when it has a low thermal conductivity.

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