Simulation of Plasto-Elastohydrodynamic Lubrication in Line Contacts of Infinite and Finite Length

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Tao He ◽  
Jiaxu Wang ◽  
Zhanjiang Wang ◽  
Dong Zhu
Keyword(s):  
Surface Roughness ◽  
Finite Length ◽  
3D Model ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Axial Direction ◽  
Contact Length ◽  
Line Contact ◽  
Line Contacts ◽  
3D Surface Topography

Line contact is common in many machine components, such as various gears, roller and needle bearings, and cams and followers. Traditionally, line contact is modeled as a two-dimensional (2D) problem when the surfaces are assumed to be smooth or treated stochastically. In reality, however, surface roughness is usually three-dimensional (3D) in nature, so that a 3D model is needed when analyzing contact and lubrication deterministically. Moreover, contact length is often finite, and realistic geometry may possibly include a crowning in the axial direction and round corners or chamfers at two ends. In the present study, plasto-elastohydrodynamic lubrication (PEHL) simulations for line contacts of both infinite and finite length have been conducted, taking into account the effects of surface roughness and possible plastic deformation, with a 3D model that is needed when taking into account the realistic contact geometry and the 3D surface topography. With this newly developed PEHL model, numerical cases are analyzed in order to reveal the PEHL characteristics in different types of line contact.

Elastohydrodynamic Lubrication Analysis of Finite Line Contact Problem With Consideration of Two Free End Surfaces

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Haibo Zhang ◽  
Wenzhong Wang ◽  
Shengguang Zhang ◽  
Ziqiang Zhao
Keyword(s):  
Contact Problem ◽  
Finite Length ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Free Boundaries ◽  
Finite Line Contact ◽  
Line Contacts ◽  
Speed Up ◽  
Finite Line ◽  
Overlapping Method

Elastohydrodynamic lubrication (EHL) analysis in finite line contacts is usually modeled by a finite-length roller contacting with a half-space, which ignores effect of the two free boundaries existing in many applications such as gears or roller bearings. This paper presents a semi-analytical method, involving the overlapping method and matrix formation, for EHL analysis in the finite line contact problem to consider the effect of two free end surfaces. Three half-spaces with mirrored loads to be solved are overlapped to cancel out the stresses at expected surfaces, and three matrices can be obtained and reused for the same finite-length space. The isothermal Reynolds equation is solved to obtain the pressure distribution and the fast Fourier transform (FFT) is used to speed up the elastic deformation and stress related calculation. Different line contact situations, including straight rollers, tapered rollers, and Lundberg profile rollers, are discussed to explore the effect of free end surfaces.

Effect of Thermal Properties of a Coated Elastohydrodynamic Lubrication Line Contact Under Various Slide-to-Roll Ratios

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Huaiju Liu ◽  
Caichao Zhu ◽  
Zonglin Gu ◽  
Zhanjiang Wang ◽  
Jinyuan Tang
Keyword(s):  
Mechanical Properties ◽  
Thermal Properties ◽  
Elastohydrodynamic Lubrication ◽  
Temperature Fields ◽  
Line Contact ◽  
Oil Film ◽  
Line Contacts ◽  
Energy Equations ◽  
Thermal Conductivities

A numerical thermal elastohydrodynamic lubrication (EHL) model is developed for coated line contacts by considering both the mechanical properties and the thermal properties of the coating and the substrate. The temperature fields within the oil film and within the solids are solved by deriving the energy equations for the solids and the oil film. Heat continuity conditions are satisfied at the interfaces between the solids and the oil film, and the coating/substrate interfaces. Effects of the slide-to-roll ratio (SR), the thermal conductivities of the coating bodies, and the oil film on temperature fields are studied.

End Effect Attenuation in Tapered Roller Contacts

2009 ◽  
Author(s):  
Emanuel Diaconescu
Keyword(s):  
Pressure Distribution ◽  
Finite Length ◽  
Contact Length ◽  
Maximum Pressure ◽  
End Effect ◽  
End Effects ◽  
Maximum Value ◽  
Line Contacts ◽  
Tapered Roller

The end effect attenuation in finite length line contacts is mainly approached for cylindrical bodies. Multi-radius crowning may remove end effects in tapered roller contacts. Another method for leveling maximum pressure in these contacts is the use of polynomial generatrix. This paper investigates the effect of this generatrix in tapered roller contacts. An improved pressure distribution is obtained. This has a nearly flat maximum value along most of contact length.

Theoretical and Experimental Investigation of Frictional and Thermal Behavior in Oscillatory Sliding Line Contact

2005 ◽  
Author(s):  
M. Mansouri ◽  
M. M. Khonsari ◽  
D. Y. Hua
Keyword(s):  
Thermal Behavior ◽  
Three Dimensional ◽  
Axial Direction ◽  
Contact Theory ◽  
Design Stage ◽  
Heat Equations ◽  
Line Contact ◽  
Test Rig ◽  
Curve Fit ◽  
Future Extension

A model is developed to predict the thermal behavior of two sliding bodies undergoing oscillatory relative motion. The thermal model is capable of predicting the temperature rise distribution within the pin-bushing pair and the housing. The bodies geometrically form a pin-bushing configuration and the Hertzian line contact theory is used to approximate the contact pressure and the width. A quasi- three dimensional temperature model is developed by averaging the temperature in the axial direction. The resulting dimensionless heat equations and proper boundary conditions are solved by the finite element method. A series of dimensionless equations for use at the design stage is presented. A test rig capable of inducing oscillatory motion under heavy loading condition is used for measuring friction and temperature. The measured coefficient of friction history, which is curve fit as a function of time, is used in the simulations. The description of the test rig, modeling aspects, and the future extension of the research comprise the contents of this paper.

A Three-Dimensional Model of Line-Contact Elastohydrodynamic Lubrication for Heterogeneous Materials with Inclusions

2016 ◽  
Vol 08 (02) ◽  
pp. 1650014 ◽  
Author(s):  
Kun Zhou ◽  
Qingbing Dong
Keyword(s):  
Film Thickness ◽  
Half Space ◽  
Surface Deformation ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Line Contact ◽  
Lubricant Film Thickness ◽  
Equivalent Inclusion Method ◽  
Surface Contact

This paper develops a three-dimensional (3D) model for a heterogeneous half-space with inclusions distributed periodically beneath its surface subject to elastohydrodynamic lubrication (EHL) line-contact applied by a cylindrical loading body. The model takes into account the interactions between the loading body, the fluid lubricant and the heterogeneous half-space. In the absence of subsurface inclusions, the surface contact pressure distribution, the half-space surface deformation and the lubricant film thickness profile are obtained through solving a unified Reynolds equation system. The inclusions are homogenized according to Eshelby’s equivalent inclusion method (EIM) with unknown eigenstrains to be determined. The disturbed half-space surface deformations induced by the subsurface inclusions or eigenstrains are iteratively introduced into the lubricant film thickness until the surface deformation finally converges. Both time-independent smooth surface contact and time-dependent rough surface contact are considered for the lubricated contact problem.

Bearing condition assessment. Part 1: Size and frequency of surface roughness interactions in impulsive vibration measurements

2003 ◽  
Vol 217 (6) ◽  
pp. 435-445 ◽  
Author(s):  
M Ho ◽  
D. J. Birch ◽  
P. J. Brunn
Keyword(s):  
Surface Roughness ◽  
Gaussian Distribution ◽  
Piezoelectric Transducer ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Two Dimensional ◽  
Rolling Bearings ◽  
Innovative Method ◽  
Lubrication Conditions ◽  
Dimensional Surface

Impulsive vibrations generated during the operation of a rolling Hertzian line contact under elastohydrodynamic lubrication (EHL) conditions, typically found in tapered rolling bearings, are analysed using two-dimensional surface roughness profiles containing spherical asperities. The cause of these vibrations is modelled as a series of collisions between the asperities forming the surfaces in contact. Asperity heights are considered to vary according to a Gaussian distribution, and an innovative method, based upon probability, is developed so that the rates and the magnitudes of collisions between asperities of various heights under different lubrication conditions can be studied. The magnitude of individual collisions are predicted to allow them to be compared with those measured using a calibrated master piezoelectric transducer.

Mixed Elastohydrodynamic Lubrication in Finite Roller Contacts Involving Realistic Geometry and Surface Roughness

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Dong Zhu ◽  
Jiaxu Wang ◽  
Ning Ren ◽  
Q. Jane Wang
Keyword(s):  
Stress Concentration ◽  
Elastohydrodynamic Lubrication ◽  
Contact Length ◽  
Operating Conditions ◽  
Engineering Practice ◽  
Dry Contact ◽  
Line Contacts ◽  
Length Direction ◽  
Principal Directions ◽  
Realistic Geometry

Concentrated (or counterformal) contacts are found in many mechanical components that transmit significant power. Traditionally, concentrated contacts can be roughly categorized to point and line contacts. In point contacts, the contact area is small in both principal directions, while in line contacts, it is small in one direction but assumed to be infinitely long in the other direction. However, these two types of geometry are results of simplification that does not precisely cover all the contact conditions in engineering practice. Actually most line contact components are purposely designed to have a crown in the contact length direction in order to accommodate possible non-uniform load distribution and misalignment. Moreover, the contact length is always finite, and at two ends of the contact there usually exist round corners or chamfers to reduce stress concentration. In the present work, the deterministic mixed EHL model developed previously has been modified to take into account the realistic geometry. Sample cases have been analyzed to investigate the effects of contact length, crowning, and end corners (or chamfers) on the EHL film thickness and the stress concentration, and also to demonstrate the entire transition from full-film and mixed EHL down to a practically dry contact under severe operating conditions with real machined roughness. It appears that this modified model can be used as an engineering tool for roller design optimization through in-depth mixed EHL performance evaluation.

Film Thickness and Asperity Load Formulas for Line-Contact Elastohydrodynamic Lubrication With Provision for Surface Roughness

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
M. Masjedi ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Reynolds Equation ◽  
Surface Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Load Ratio ◽  
Material Surface ◽  
Line Contact ◽  
Wide Range ◽  
Minimum Film Thickness

Three formulas are derived for predicting the central and the minimum film thickness as well as the asperity load ratio in line-contact EHL with provision for surface roughness. These expressions are based on the simultaneous solution to the modified Reynolds equation and surface deformation with consideration of elastic, plastic and elasto-plastic deformation of the surface asperities. The formulas cover a wide range of input and they are of the form f(W, U, G, σ¯, V), where the parameters represented are dimensionless load, speed, material, surface roughness and hardness, respectively.

Optimum design of the roller profile based on the elastohydrodynamic lubrication model

2019 ◽  
Vol 233 (10) ◽  
pp. 1594-1604
Author(s):  
Zhijian Wang ◽  
Xiaoyang Chen ◽  
Xuejin Shen ◽  
Liye Zhou
Keyword(s):  
Fatigue Life ◽  
Pressure Distribution ◽  
Optimum Design ◽  
Finite Length ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Profile Modification ◽  
Life Tests ◽  
Roller Profile

Roller profile modification is often used to unify the pressure distribution and to prolong the life of the roller. In this paper, the formula of the optimum modification coefficient for the logarithmically profiled roller is derived to design the roller profile based on the elastohydrodynamic lubrication model of finite-length line contact. In order to demonstrate the feasibility of this formula, a set of fatigue life tests was conducted. The results show that the optimum roller profile predicted by the presented formula can provide the longest fatigue life. Thus, this method can be directly applied.

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