Numerical investigation on single dent in EHL point contacts

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Qiancheng Qin ◽  
Xue-Feng Wang ◽  
Rufu Hu ◽  
Xiaomin Cheng
Keyword(s):  
Film Thickness ◽  
Maximum Pressure ◽  
Point Contacts ◽  
Governing Equations ◽  
Content Type ◽  
Entrainment Velocity ◽  
Minimum Film Thickness ◽  
Input Parameters ◽  
Pressure Peak ◽  
Lubricating Properties

Purpose This study aims to investigate the effects of single dent on the film thickness and pressure in elastohydrodynamically lubricated (EHL) point contacts by numerical analysis. Design/methodology/approach The governing equations of single dent were established and then the variations of the film thickness and pressure induced by the applied load, the entrainment velocity and the ball radius were investigated. Meanwhile, the film thickness and pressure under smooth and dented surfaces were compared with each other. Findings The dent enhances both the maximum pressure and the second pressure peak. The minimum film thickness arises before the dent under certain conditions. In the meantime, the pressure decreases at the inside of the dent and the film thickness is just the reverse. The entrainment velocity remarkably affects the overall film thickness, whereas the rest of the input parameters mainly decides the details of the film curve. All input parameters remarkably affect the overall pressure, especially the maximum pressure. Originality/value This work is helpful to understanding the effect of the single dent on the lubricating properties of EHL point contacts.

On the crucial role of ellipticity on elastohydrodynamic film thickness and friction

2016 ◽  
Vol 230 (12) ◽  
pp. 1503-1515 ◽  
Author(s):  
J-D Wheeler ◽  
N Fillot ◽  
P Vergne ◽  
D Philippon ◽  
GE Morales Espejel
Keyword(s):  
Film Thickness ◽  
Maximum Pressure ◽  
Fluid Viscosity ◽  
Point Contacts ◽  
Entrainment Velocity ◽  
Minimum Film Thickness ◽  
Elliptical Contact ◽  
Thickness Variations ◽  
Poiseuille Flows

The study reported here deals with elastohydrodynamic point contacts and it is focused on the influence of contact ellipticity. In five velocity–load reference cases, ellipticity was varied from slender to wide configurations, including the circular contact. For each case, Hertzian pressure, Hertzian area, load, and entrainment velocity were kept constant while the ellipticity was varied by changing the curvature radii. In this context, the maximum central film thickness did not occur for the infinitely wide contact, but for a slender configuration close to the circular case. Moreover, the minimum film thickness reached its optimum for a wide but finite elliptical contact. For low ellipticity ratios, specific film thickness features were obtained. In particular, very high central/minimum film thickness ratios are found. The cause of these behaviors was found in the change of the convergent shape. When the ellipticity was varied, the Poiseuille flows parallel and transverse to the entrainment direction were significantly modified and these modifications were quantitatively analyzed for the different cases. The competition between the Couette and the Poiseuille flows was totally different between the narrow and the wide elliptical contact, and this change was responsible for the film thickness variations with ellipticity. Ellipticity also had an effect on friction as it influenced the maximum pressure which in turn impacts the fluid viscosity.

Effects of reciprocating motion parameters on lubricating properties of tripod sliding universal joints

2014 ◽  
Vol 66 (1) ◽  
pp. 111-123 ◽  
Author(s):  
X.F. Wang ◽  
R.F. Hu ◽  
K.S. Wang ◽  
H.R. Cui
Keyword(s):  
Film Thickness ◽  
Geometrical Model ◽  
Reciprocating Motion ◽  
Content Type ◽  
Entrainment Velocity ◽  
Pressure Peak ◽  
New Type ◽  
Sweeping Method ◽  
Motion Parameters ◽  
Bounding Surfaces

Purpose – This paper aims to clarify the effects of the reciprocating motion parameters on the lubricating performance of the tripod sliding universal joint (TSUJ). These parameters mainly include the frequency and amplitude of the reciprocating motion. This work will explain how the film thickness and pressure as well as the temperature vary with the frequency and amplitude of the reciprocating motion in order to improve the lubricating performance of the TSUJ and extend its working life. Design/methodology/approach – Based on the simplified geometrical model derived from the main mating surfaces, the effects of the frequency and amplitude on the pressure and film thickness as well as the temperature are theoretically investigated. In this work, multi-level method, multilevel multi-integration method and sequential line sweeping method were applied to solving Reynolds equation, the elastic deformation of the bounding surfaces and temperature, respectively. Findings – The overall film thickness increases with the increase of the amplitude or frequency. The consumed time of the rippled film passing through the contact zone hardly depends on the amplitude or frequency. The variation of the film or temperature lags behind the variation of the entrainment velocity. Increasing amplitude or frequency increases the temperature. The effect of the amplitude or frequency on the pressure focuses mainly on the second pressure peak. Originality/value – TSUJ is a new-type tripod joint and the obtained results are of great value for its design and application.

Transient elastohydrodynamic lubrication analysis of spur gears running-in considering effects of solid particles and surface roughness

2016 ◽  
Vol 68 (2) ◽  
pp. 183-190 ◽  
Author(s):  
Xingbao Huang ◽  
Youqiang Wang
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Solid Particles ◽  
Maximum Pressure ◽  
Spur Gears ◽  
Content Type ◽  
Lubrication Performance ◽  
Minimum Film Thickness ◽  
Variant Effect

Purpose – This paper aims to investigate the mechanism of spur gears running-in and to solve the lubrication problems of teeth running-in. Design/methodology/approach – The elastohydrodynamic lubrication (EHL) model considering solid particles was established by applying multi-grid and multiple-grid integration methods to the numerical solution. Findings – In the region where debris settle, transient pressure increases sharply, and a noticeable increase in the running-in load causes a remarkable increase in both the centre and maximum pressures and a slight increase in the minimum film thickness. Roughness wavelength makes a considerable difference to the minimum film thickness at double-to-single tooth transient. A considerable increase in rotation velocity can cause a remarkable reduction in both the centre and maximum pressures but an amazing increase in the minimum film thickness. The effects of roughness amplitude on the maximum pressure are considerably distinct. Research limitations/implications – Research on EHL of spur gears in the running-in process considering solid particles, surface roughness and time-variant effect is meaningful to practical gears running-in. Thermal effect can be included in the next study. Practical implications – The analysis results can be applied to predict and improve lubrication performance of the meshing teeth. Social implications – The aim is to reduce gears’ manufacture and running-in costs and improve economic performance. Originality/value – The EHL model that considers solid particles was established. The Reynolds equation was deduced taking the effects of solid particles into account. The EHL of spur gears running-in was investigated considering the time-variant effect, surface roughness, running-in load and rotation speed.

Dynamic Analysis of Tilting-Pad Journal Bearing—Influence of Pad Deformations

1994 ◽  
Vol 116 (3) ◽  
pp. 621-627 ◽  
Author(s):  
H. Desbordes ◽  
M. Fillon ◽  
C. Chan Hew Wai ◽  
J. Frene
Keyword(s):  
Film Thickness ◽  
Pressure Field ◽  
Journal Bearing ◽  
Maximum Pressure ◽  
Tilting Pad ◽  
Minimum Film Thickness ◽  
Dimensional Finite Element ◽  
The One ◽  
Tilting Pad Journal Bearing ◽  
Tilting Pad Journal Bearings

A theoretical nonlinear analysis of tilting-pad journal bearings is presented for small and large unbalance loads under isothermal conditions. The radial displacements of internal pad surface due to pressure field are determined by a two-dimensional finite element method in order to define the actual film thickness. The influence of pad deformations on the journal orbit, on the minimum film thickness and on the maximum pressure is studied. The effects of pad displacements are to decrease the minimum film thickness and to increase the maximum pressure. The orbit amplitude is also increased by 20 percent for the large unbalance load compared to the one obtained for rigid pad.

Comprehensive design methodology for an engine journal bearing

2000 ◽  
Vol 214 (4) ◽  
pp. 401-412 ◽  
Author(s):  
H Hirani ◽  
K Athre ◽  
S Biswas
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Design Methodology ◽  
Design Procedure ◽  
Maximum Pressure ◽  
Connecting Rod ◽  
Automotive Engine ◽  
Reciprocating Engine ◽  
High Power Output ◽  
Minimum Film Thickness

The trend towards high power output, high speed and low power loss in engines requires a better understanding of bearing behaviour. Research in this area is directed more towards different aspects involved in bearing analyses, rather than providing a comprehensive guideline on design of bearing. This effort compiles the design methodology for selection of diametral clearance and bearing length by limiting the minimum film thickness, maximum pressure and temperature. The design procedure is summarized on the basis of the existing rapid bearing analyses for evaluation of the journal trajectory, minimum film thickness and maximum pressure and simplified thermal analysis. A flow chart is provided for step-by-step bearing design. Finally, two case studies of engine bearings are described: one investigates the VEB bigend connecting-rod bearing for a large industrial reciprocating engine and the other a main crankshaft bearing for an automotive engine. The methodology translates into easy-to-use expressions and the overall procedure is outlined, using practical data to demonstrate how this can be employed effectively by users.

Influence of Scratches on the Performance of a Partial Journal Bearing

2008 ◽  
Author(s):  
Mihai B. Dobrica ◽  
Michel Fillon
Keyword(s):  
Film Thickness ◽  
Thermal Effects ◽  
Journal Bearing ◽  
Friction Torque ◽  
Maximum Pressure ◽  
Relative Depth ◽  
Performance Loss ◽  
Minimum Film Thickness ◽  
Overall Performance ◽  
Bearing Damage

In this paper, the influence of circumferential scratches on the thermohydrodynamic performance of a partial (lobe) journal bearing is studied. The bearing damage is characterized by four factors: the area of the scratched region, the density of the scratches within the affected area, the relative position of the scratched region and the relative depth of the wear defects. The bearing performance is characterized by minimum film thickness, average oil temperature, maximum pressure, friction torque etc., at imposed magnitude and direction of the load. A numerical hydrodynamic model with global thermal effects is used for studying the influence of the different wear related parameters on the bearing performance. The results permit to predict the overall performance loss due to the circumferential wear marks, for different wear profiles. The types of wear profiles that can lead to the bearing destruction (characterized by a critical minimum film thickness) are also investigated.

An Experimental Analysis of Misalignment Effects on Hydrodynamic Plain Journal Bearing Performances

2001 ◽  
Vol 124 (2) ◽  
pp. 313-319 ◽  
Author(s):  
J. Bouyer ◽  
M. Fillon
Keyword(s):  
Film Thickness ◽  
Journal Bearing ◽  
Hydrodynamic Pressure ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Maximum Pressure ◽  
Minimum Film Thickness ◽  
Oil Flow ◽  
Hydrodynamic Effects

The present study deals with the experimental determination of the performance of a 100 mm diameter plain journal bearing submitted to a misalignment torque. Hydrodynamic pressure and temperature fields in the mid-plane of the bearing, temperatures in two axial directions, oil flow rate, and minimum film thickness, were all measured for various operating conditions and misalignment torques. Tests were carried out for rotational speeds ranging from 1500 to 4000 rpm with a maximum static load of 9000 N and a misalignment torque varying from 0 to 70 N.m. The bearing performances were greatly affected by the misalignment. The maximum pressure in the mid-plane decreased by 20 percent for the largest misalignment torque while the minimum film thickness was reduced by 80 percent. The misalignment caused more significant changes in bearing performance when the rotational speed or load was low. The hydrodynamic effects were then relatively small and the bearing offered less resistance to the misalignment.

Roughness Amplitude Reduction Under Non-Newtonian EHL Conditions

2005 ◽  
Author(s):  
A. D. Chapkov ◽  
C. H. Venner ◽  
A. A. Lubrecht
Keyword(s):  
Film Thickness ◽  
Pressure Fluctuations ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Quantitative Prediction ◽  
Point Contacts ◽  
Minimum Film Thickness ◽  
Roughness Amplitude ◽  
Average Film Thickness ◽  
Ehl Contact

The influence of surface roughness on the performance of bearings and gears operating under ElastoHydrodynamic Lubrication (EHL) conditions has become increasingly important over the last decade, as the average film thickness decreased due to various influences. Surface features can reduce the minimum film thickness and thus increase the wear. They can also increase the temperature and the pressure fluctuations, which directly affects the component life. In order to describe the roughness geometry inside an EHL contact, the amplitude reduction of harmonic waviness has been studied over the last ten years. This theory currently allows a quantitative prediction of the waviness amplitude and includes the influence of wavelength and contact operating conditions. However, the model assumes a Newtonian behaviour of the lubricant. The current paper makes a first contribution to the extension of the roughness amplitude reduction for EHL point contacts including non-Newtonian effects.

A thermal EHL investigation on plate-pin hinge pairs in silent chains using a narrow finite line contact

2020 ◽  
Vol 72 (10) ◽  
pp. 1139-1145
Author(s):  
Mingyu Zhang ◽  
Jing Wang ◽  
Jinlei Cui ◽  
Peiran Yang
Keyword(s):  
Film Thickness ◽  
Temperature Rise ◽  
Elastohydrodynamic Lubrication ◽  
Radius Of Curvature ◽  
Line Contact ◽  
Equivalent Radius ◽  
Content Type ◽  
Finite Line Contact ◽  
Pressure Peak ◽  
Finite Line

Purpose The purpose of this paper is to numerically study the variations of oil film pressure, thickness and temperature rise in the contact zone of plate-pin pair in silent chains. Design/methodology/approach A steady-state thermal elastohydrodynamic lubrication (EHL) model is built using a Ree–Eyring fluid. The contact between the plate and the pin is simplified as a narrow finite line contact, and the lubrication state is examined by varying the geometry and the plate speed. Findings With increase in the equivalent radius of curvature, the pressure peak and the central film thickness increase. Because the plate is very thin, the temperature rise can be neglected. Even when the influence of the rounded corner region is less, a proper design can beneficially increase the minimum film thickness at both edges of the plate. Under a low entraining speed, strong stress concentration results in close-zero film thickness at both edges of the plate. Originality/value This study reveals the EHL feature of the narrow finite line contact in plate-pin pairs for silent chains and will support the future works considering transient effect, surface features and wear.

Study on curved surface design of sliding pair based on stepped topography model

2019 ◽  
Vol 72 (1) ◽  
pp. 86-92 ◽  
Author(s):  
Zhenpeng Wu ◽  
Vanliem Nguyen ◽  
Zhihong Zhang ◽  
Liangcai Zeng
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Liquid Film ◽  
Bearing Capacity ◽  
Fluid Film ◽  
Curved Surface ◽  
Surface Model ◽  
Content Type ◽  
Lubrication Performance ◽  
Minimum Film Thickness

Purpose The stepped topography of the friction pairs mainly causes the fluid film thickness to change in the direction of motion. In this region, there have very few topographical design methods for continuous or non-linear distribution of the fluid film. The purpose of this study is to analyze the effect of the curved surface on the performance of the liquid film. Design/methodology/approach First, a numerical simulation is used to solve the optimal bearing capacity and friction coefficient of the liquid film under the condition of the minimum film thickness. Then, the curved surface described by the sinusoidal curve equation is applied in the transitional region of maximum and minimum film thickness. The bearing capacity and the friction coefficient of the liquid film are respectively simulated and compared in the same condition of the minimum film thickness. Findings The research results show that the liquid film using the curved surface transition model, the optimal bearing capacity is significantly increased by 32 per cent while the optimal friction coefficient is clearly reduced by 38 per cent in comparison with using stepped surface model. Originality/value The friction pair with curved transition enables better lubrication performance of the liquid film and better adaptability under unstable conditions.

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