Computational approaches for modelling elastohydrodynamic lubrication using multiphysics software

2012 ◽  
Vol 226 (6) ◽  
pp. 463-480 ◽  
Author(s):  
Xincai Tan ◽  
Christopher E Goodyer ◽  
Peter K Jimack ◽  
Robert I Taylor ◽  
Mark A Walkley
Keyword(s):  
Engineering Design ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Relative Performance ◽  
Solution Strategy ◽  
Computational Approaches ◽  
Involute Gear ◽  
Transient Case ◽  
Mechanical Components ◽  
Lubrication Conditions

Elastohydrodynamic lubrication modelling plays an important role in engineering design and analysis, since a number of important mechanical components operate under elastohydrodynamic lubrication conditions. In this article, methods are presented for solving both line and point contact cases using multiphysics software. The advantages, and the overheads, of using such an approach over developing highly specialised, bespoke software are highlighted. In order to calculate the deformation of the contacts three different methods are developed and their relative performance is assessed. The advantage of using a nested solution strategy has also been examined. The flexibility of the multiphysics software approach is highlighted in results involving a complex transient case modelling an involute gear.

Traction behaviour of elastohydrodynamic lubrication films with anomalous shapes

2021 ◽  
pp. 135065012199724
Author(s):  
Kazuyuki Yagi ◽  
Kazuki Nishida ◽  
Joichi Sugimura
Keyword(s):  
Ethylene Glycol ◽  
Gradual Increase ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Conventional Film ◽  
Lubricant Films ◽  
Traction Coefficient ◽  
Traction Fluids ◽  
Sapphire Disc ◽  
Lubrication Conditions

This study describes traction behaviours of lubricant films having anomalous shapes under elastohydrodynamic lubrication conditions. The traction generated at a point contact area between a glass or sapphire disc and a steel ball was measured by changing the slide-to-roll ratio. Three alcohols, 1-dodecanol, ethylene glycol and glycerol, and two alkanes of n-tetradecane and n-hexadecane were used as lubricants. Lubricants developing anomalous film shapes exhibited a solid-like behaviour with a sharp traction peak at low slide-to-roll ratios. On the contrary, other lubricants having conventional film shapes indicated a gradual increase in traction coefficient with increasing slide-to-roll ratios. The similarity of the traction behaviour to that of traction fluids supports the solidification of the film, which developed anomalous film shapes.

scholarly journals A thermal resistances-based approach for thermal-elastohydrodynamic calculations in point contacts

2017 ◽  
Vol 232 (11) ◽  
pp. 2088-2102 ◽  
Author(s):  
Eduardo de la Guerra Ochoa ◽  
Javier Echávarri Otero ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Thermal Effects ◽  
Good Accuracy ◽  
Computational Cost ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
New Approach ◽  
Ball On Disc

This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction coefficient in the contact is estimated, along with the distribution of both film thickness and temperature. A commercial tribometer is used in order to measure the friction coefficient at a ball-on-disc point contact lubricated with a polyalphaolefin base. These data and other experimental results available in the bibliography are compared to those obtained by using the proposed methodology, and thermal effects are analysed. The new approach shows good accuracy for predicting the friction coefficient and requires less computational cost than full thermal-elastohydrodynamic simulations.

Mechanical Power Losses of Ball Bearings: Model and Experimental Validation

2021 ◽  
pp. 1-29
Author(s):  
Ahmet Dindar ◽  
Amit Chimanpure ◽  
Ahmet Kahraman
Keyword(s):  
Dynamic Model ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Mechanical Power ◽  
Ball Bearings ◽  
Power Losses ◽  
Euler Parameters ◽  
Surface Shear ◽  
Axial Forces ◽  
Set Up

Abstract A tribo-dynamic model of ball bearings is proposed to predict their load-dependent (mechanical) power losses. The model combines (i) a transient, point contact mixed elastohydrodynamic lubrication (EHL) formulation to simulate the mechanics of the load carrying lubricated ball-race interfaces, and (ii) a singularity-free dynamics model, and establishes the two-way coupling between them that dictates power losses. The dynamic model employs a vectoral formulation with Euler parameters. The EHL model is capable of capturing two-dimensional contact kinematics, velocity variations across the contact as well as asperity interactions of rough contact surfaces. Resultant contact surface shear distributions are processed to predict mechanical power losses of example ball bearings operating under combined radial and axial forces. An experimental set-up is introduced for measurement of the power losses of rolling-element bearings. Sets of measurements taken by using the same example ball bearings are compared to those predicted by the model to assess its accuracy in predicting mechanical power loss of a ball bearing within wide ranges of axial and radial forces.

Experimental and numerical study on cavitation under elastohydrodynamic lubrication point contact

2021 ◽  
pp. 135065012110527
Author(s):  
Mingfei Ma ◽  
Wen Wang ◽  
Wenxun Jiang
Keyword(s):  
Contact Area ◽  
Numerical Study ◽  
Ambient Pressure ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hertzian Contact ◽  
Pressure Area ◽  
Cavitation Pressure ◽  
Experimental Researches ◽  
State 1

As a common phenomenon in elastohydrodynamic lubrication, cavitation has an effect on the completeness of the oil film in the contact area. Many studies have therefore been conducted on cavitation. Experimental researches on cavitation usually rely on optical interference observation, which offers a limited resolution and observation range. In this paper, an infrared thermal camera is used to observe the cavity bubbles on a ball-on-disc setup under sliding/rolling conditions. The results show that the cavity length increases with an increases of the entrainment speed and the viscosity of the lubricants. These observations are explained by a numerical model based on Elrod's algorithm. Effects of entrainment speed and lubricant viscosity on the breakup of cavitation bubbles and the cavitation states are investigated. Both the simulation and experimental results show that a negative pressure area is present behind the Hertzian contact area. The ambient pressure plays a role in maintaining cavitation state 1. The cavitation pressure is close to the vacuum pressure when the entrainment speed is low and to the ambient pressure instead when the entrainment speed is high.

Scale Effects in Generalized Newtonian Elastohydrodynamic Films

2008 ◽  
Author(s):  
I. I. Kudish ◽  
P. Kumar ◽  
M. M. Khonsary ◽  
S. Bair
Keyword(s):  
Film Thickness ◽  
Scale Effects ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Viscosity Coefficient ◽  
Shear Thinning ◽  
Effective Pressure ◽  
Practical Advantage ◽  
Inlet Zone ◽  
Real Machine

The prediction of elastohydrodynamic lubrication (EHL) film thickness requires knowledge of the lubricant properties. Today, in many instances, the properties have been obtained from a measurement of the central film thickness in an optical EHL point contact simulator and the assumption of a classical Newtonian film thickness formula. This technique has the practical advantage of using an effective pressure-viscosity coefficient which compensates for shear-thinning. We have shown by a perturbation analysis and by a full EHL numerical solution that the practice of extrapolating from a laboratory scale measurement of film thickness to the film thickness of an operating contact within a real machine may substantially overestimate the film thickness in the real machine if the machine scale is smaller and the lubricant is shear-thinning in the inlet zone.

Thermal Elastohydrodynamic Lubrication Analysis for Point Contact Transmission

2009 ◽  
Author(s):  
Hai-zhou Huang ◽  
Xi-chuan Niu ◽  
Xiao-yang Yuan
Keyword(s):  
Film Thickness ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Surface Velocity ◽  
Squeeze Film ◽  
Elastic Displacement ◽  
Circular Arc ◽  
Tooth Width ◽  
Contact Transmission

To investigate the thermal EHL (elastohydrodynamic lubrication) in point contact transmission, a model considering the two-dimensional surface velocity of tooth face and the running-in is proposed. The numerical solutions for pressure, temperature and film thickness distribution in the contact zone are obtained by solving equations including the Reynolds, Energy and the elastic displacement with variable dimension meshing method. The model was used to study the point contact transmission of the circular arc gear in a windlass. The main results show that it is pure rolling along the direction of tooth width, and the rolling speed plays a leading role in improving the lubricating performance and transmission efficiency of circular arc gear. The squeeze film effect makes the pressure peak tend to be gentle and the film thickness increase slightly.

Effect of tooth waist order parameters of double involute gears on lubrication performance of gear drive

2016 ◽  
Vol 68 (6) ◽  
pp. 671-675 ◽  
Author(s):  
Zhimin Fan ◽  
Wanfeng Zhou ◽  
Ruixue Wang ◽  
Na Wang
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Reference Value ◽  
Tooth Profile ◽  
Order Parameters ◽  
Content Type ◽  
Oil Film ◽  
Gear Drive ◽  
Involute Gear ◽  
Lubrication Performance ◽  
Involute Gears

Purpose The purpose of this paper is to derive a new lubrication model of double involute gears drive and study the effect of the tooth waist order parameters of double involute gears on lubrication performance. Design/methodology/approach The new lubrication model of double involute gears drive was established according to the meshing characteristics of double involute gears drive and the finite length line contact elastohydrodynamic lubrication theory. Numerical calculation of the lubrication model of gear drive was conducted using the multigrid method. Findings The results show that the oil film necking phenomenon and the oil film pressure peak emerged at the tooth waist order area and the tooth profile ends, and when compared with involute gear, the lubrication performance at the tooth waist order area is better than that at the tooth profile ends. The effect of tooth waist order parameters on lubrication performance at the tooth waist order area was greater than that at other areas. Originality/value This research will promote the application of the double involute gear as soon as possible, and it has the reference value for other types of gears.

Theoretical and experimental studies of the oil film in lubricated point contact

1966 ◽  
Vol 291 (1427) ◽  
pp. 520-536 ◽  
Keyword(s):  
Surface Layer ◽  
Film Thickness ◽  
Strong Evidence ◽  
Experimental Studies ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Experimental Results ◽  
Point Contacts ◽  
Previous Theory ◽  
Oil Film

A technique using Newton’s rings for mapping the oil film of lubricated point contacts is described. A theoretical value for the film thickness of such contacts in elastohydrodynamic lubrication is derived. The experimental results give the exit constriction predicted by previous theory but never shown in detail. The comparison of theoretical and experimental oil film thicknesses, which is satisfactorily accurate, gives strong evidence for a viscous surface layer some 1000Å thick. This film agrees with the known ‘lubricating power’ of the various oils tested.

A simplified approach for thermal elastohydrodynamic lubrication analysis of circular contacts using realistic lubricant properties

2018 ◽  
Vol 232 (12) ◽  
pp. 1618-1632
Author(s):  
Puneet Katyal ◽  
Punit Kumar
Keyword(s):  
Mathematical Models ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Computation Time ◽  
Fluid Temperature ◽  
Simplified Approach ◽  
Lubrication Film ◽  
Isothermal Case ◽  
Lubrication Characteristics ◽  
Time Required

Thermal effect in elastohydrodynamic lubrication has been the subject of extensive research for several decades. The focus of this study was primarily on the development of an efficient numerical scheme to deal with the computational challenges involved in the solution of thermal elastohydrodynamic lubrication model; however, some important aspects related to the accurate description of lubricant properties such as viscosity, rheology, and thermal conductivity in elastohydrodynamic lubrication point contact analysis remain largely neglected. A few studies available in this regard are based upon highly complex mathematical models difficult to formulate and execute. The end-users may not have the specialized skill, knowledge, and time required for the development of computational codes pertaining to these models. Therefore, this paper offers a very simple approach to determine the distribution of mean fluid temperature within an elastohydrodynamic lubrication film. While it is an approximate method, it yields reasonably accurate results with only a little increase in computation time with respect to the isothermal case. Moreover, it can be added as a small module to any existing isothermal algorithm. Using this simplified thermal elastohydrodynamic lubrication model for point contacts, this work sheds some light on the importance of accurate characterization of the lubricant properties and demonstrates that the computed thermal elastohydrodynamic lubrication characteristics are highly sensitive to lubricant properties. It also emphasizes the use of appropriate mathematical models with experimentally determined parameters to account for the correct lubricant behavior.

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