A Mixed-TEHD Model for Journal-Bearing Conformal Contacts—Part I: Model Formulation and Approximation of Heat Transfer Considering Asperity Contact

1998 ◽  
Vol 120 (2) ◽  
pp. 198-205 ◽  
Author(s):  
Fanghui Shi ◽  
Qian (Jane) Wang
Keyword(s):  
Heat Transfer ◽  
Mixed Lubrication ◽  
Integrated System ◽  
Asperity Contact ◽  
Model Formulation ◽  
Roughness Effect ◽  
Elastic Process ◽  
Numerical Process ◽  
Large Eccentricity ◽  
Lubrication Conditions

A mixed-TEHD (thermal elastohydrodynamic) model was developed for journal bearings working at large eccentricity ratios in order to facilitate a better understanding of mixed-lubrication phenomena for conformal-contact elements. The model consists of a mixed-lubrication process that considers the roughness effect and asperity contact, a thermal process for temperature analyses, and a thermal-elastic process for deformation calculations. In this model, the interactive journal, lubricant, and bearing were treated as an integrated system. Finite-element, finite-difference, and influence-function methods were utilized in the numerical process. The overall solution was achieved by the iteration method. Analyses of a simulated bearing-lubricant-journal system working under mixed-lubrication conditions were conducted, and the influence of the changes of lubricant flows as a result of the asperity contact on the system heat transfer and temperature distributions was numerically investigated.

scholarly journals Contact stiffness and damping of spiral bevel gears under transient mixed lubrication conditions

Friction ◽  
2021 ◽  
Author(s):  
Zongzheng Wang ◽  
Wei Pu ◽  
Xin Pei ◽  
Wei Cao
Keyword(s):  
Contact Stiffness ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Spiral Bevel Gears ◽  
Bevel Gears ◽  
Dry Contact ◽  
Spiral Bevel ◽  
Stiffness And Damping ◽  
Lubrication Conditions ◽  
Film Lubrication

AbstractExisting studies primarily focus on stiffness and damping under full-film lubrication or dry contact conditions. However, most lubricated transmission components operate in the mixed lubrication region, indicating that both the asperity contact and film lubrication exist on the rubbing surfaces. Herein, a novel method is proposed to evaluate the time-varying contact stiffness and damping of spiral bevel gears under transient mixed lubrication conditions. This method is sufficiently robust for addressing any mixed lubrication state regardless of the severity of the asperity contact. Based on this method, the transient mixed contact stiffness and damping of spiral bevel gears are investigated systematically. The results show a significant difference between the transient mixed contact stiffness and damping and the results from Hertz (dry) contact. In addition, the roughness significantly changes the contact stiffness and damping, indicating the importance of film lubrication and asperity contact. The transient mixed contact stiffness and damping change significantly along the meshing path from an engaging-in to an engaging-out point, and both of them are affected by the applied torque and rotational speed. In addition, the middle contact path is recommended because of its comprehensive high stiffness and damping, which maintained the stability of spiral bevel gear transmission.

A Computer Thermal Model of Mixed Lubrication in Point Contacts

2004 ◽  
Vol 126 (1) ◽  
pp. 162-170 ◽  
Author(s):  
Wen-Zhong Wang ◽  
Yu-Chuan Liu ◽  
Hui Wang ◽  
Yuan-Zhong Hu
Keyword(s):  
Surface Temperature ◽  
Thermal Model ◽  
Reynolds Equation ◽  
Equation System ◽  
Mixed Lubrication ◽  
Successful Implementation ◽  
Asperity Contact ◽  
Point Contacts ◽  
Wide Range ◽  
Lubrication Conditions

This paper presents a transient thermal model for mixed lubrication problems in point contacts. The model deterministically calculates pressure and surface temperature by simultaneously solving a system of equations that govern the lubrication, contact and thermal behaviors of a point contact interface. The pressure distribution on the entire computation domain is obtained through solving a unified Reynolds equation system without identifying hydrodynamic or asperity contact regions. The point heat source integration method is applied to determine the temperature distributions on contact surfaces. The interactions between pressure and temperature are considered through incorporating viscosity-temperature and density-temperature relations in the Reynolds equation, then solving the equation system iteratively. With the successful implementation of an FFT-based algorithm (DC-FFT) for calculation of surface deformation and temperature rise, the numerical analysis of lubricated contact problems, which used to involve a great deal of computation, can be performed in acceptable time. The model enables us to simulate various lubrication conditions, from full film elastohydrodynamic lubrication (EHL) to boundary lubrication, for a better understanding of the effect of surface roughness. Numerical examples are analyzed and the results show that the present model can be used to predict pressure and surface temperature over a wide range of lubrication conditions, and that the solution methods are computationally efficient and robust.

Modeling of Mixed Lubrication Conditions in a Heavy Duty Piston Pin Joint

2006 ◽  
Author(s):  
Vladimir Fridman ◽  
Ilya Piraner ◽  
Kent Clark
Keyword(s):  
Contact Pressure ◽  
Hydrodynamic Pressure ◽  
Mixed Lubrication ◽  
Production Test ◽  
Asperity Contact ◽  
Connecting Rod ◽  
Test Analysis ◽  
Pressure Distributions ◽  
Contact Formulation ◽  
Lubrication Conditions

A piston pin joint in a modern diesel engine operates under extreme loading and lubrication conditions. High load in combination with low relative surface velocities and limited lubrication makes this joint prone to localized wear and sudden failure. The analysis of this joint is also complicated with the pin motion, which defines surface velocities in the pin bore to pin and the pin to connecting rod interfaces. Therefore, the entire joint needs to be analyzed as a system of two bearings. Also, the hydrodynamic pressure in this joint at times may not be sufficient to balance the force applied to the joint and has to be complemented by the asperity contact pressure. The latter causes an additional deformation of the bearing. To address this problem a mixed lubrication model has been developed based on spectral EHD and nonlinear Greenwood and Trip statistical asperity contact formulation. Contact pressure distributions calculated with this model showed a pattern similar to the wear pattern in the bushing after production test. Analysis of the heat generated in the bearing was found to be a good indicator for the severity of the regime. Analysis of the bushing and piston bore with different geometry showed that asperity contact pressure and heat generated in the joint can be significantly reduced by modifications in local shape of the contacting surfaces.

Numerical and experimental study on the effect of surface texture with roughness orientation considered under a mixed lubrication state

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Junru Wang ◽  
Quandai Wang ◽  
Yueyan Li ◽  
Meiling Guo ◽  
Pengyang Li ◽  
...  
Keyword(s):  
Surface Texture ◽  
Surface Texturing ◽  
Mixed Lubrication ◽  
Laser Surface ◽  
Geometric Parameters ◽  
Laser Surface Texturing ◽  
Textured Surface ◽  
Asperity Contact ◽  
Content Type ◽  
Texture Parameters

Purpose The purpose of this paper is to investigate the effects of surface texture with roughness orientation considered on tribological properties under a mixed lubrication state numerically and experimentally. Design/methodology/approach Based on the average Reynolds equation and asperity contact model, the impacts of surface texture parameters and roughness orientation on lubrication properties have been calculated using finite difference method. Tin–bronze samples with various prescribed surface texture geometric parameters and roughness orientation were fabricated by laser surface texturing technique, and the tribology performance of the textured surface was studied experimentally. Findings The effects of surface geometric parameters and roughness orientation parameters have been discerned. The experimental observations are in good agreement with the numerical prediction, which suggests that the numerical scheme adopted in this work is suitable in capturing the surface texture and roughness effect under mixed lubrication state. Originality/value By meticulously controlling the surface roughness and surface texture geometric characteristics based on the laser surface texturing process, samples with prescribed surface texture parameters and roughness orientation consistent with that in theoretical studies were fabricated and the theoretical model and results were verified experimentally.

Numerical Modeling of Mixed Lubrication and Flash Temperature in EHL Elliptical Contacts

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Neelesh Deolalikar ◽  
Farshid Sadeghi ◽  
Sean Marble
Keyword(s):  
Surface Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Lubrication Regime ◽  
Predicting Performance ◽  
Pure Rolling ◽  
Rolling Element ◽  
Contact Pressures ◽  
Film Lubrication

Highly loaded ball and rolling element bearings are often required to operate in the mixed elastohydrodynamic lubrication regime in which surface asperity contact occurs simultaneously during the lubrication process. Predicting performance (i.e., pressure, temperature) of components operating in this regime is important as the high asperity contact pressures can significantly reduce the fatigue life of the interacting components. In this study, a deterministic mixed lubrication model was developed to determine the pressure and temperature of mixed lubricated circular and elliptic contacts for measured and simulated surfaces operating under pure rolling and rolling/sliding condition. In this model, we simultaneously solve for lubricant and asperity contact pressures. The model allows investigation of the condition and transition from boundary to full-film lubrication. The variation of contact area and load ratios is examined for various velocities and slide-to-roll ratios. The mixed lubricated model is also used to predict the transient flash temperatures occurring in contacts due to asperity contact interactions and friction. In order to significantly reduce the computational efforts associated with surface deformation and temperature calculation, the fast Fourier transform algorithm is implemented.

scholarly journals The acoustic emission from asperity interactions in mixed lubrication

2019 ◽  
Vol 475 (2227) ◽  
pp. 20180900 ◽  
Author(s):  
S. Hutt ◽  
A. Clarke ◽  
R. Pullin ◽  
H. P. Evans
Keyword(s):  
Acoustic Emission ◽  
Wide Spectrum ◽  
Gear Tooth ◽  
Surface Film ◽  
Mixed Lubrication ◽  
Contact Voltage ◽  
Mixed Lubrication Regime ◽  
Gear Contact ◽  
All Speeds ◽  
Lubrication Conditions

Gears typically operate in mixed lubrication conditions, where the lubricant film is too thin to prevent opposing surface asperities from interacting with each other. The likelihood/intensity of interactions is indicated by the Λ ratio: the ratio of smooth surface film thickness to surface roughness. Researchers have asserted that asperity interactions are the predominant cause of acoustic emission (AE) in healthy gear contacts. However, direct experiments on gears have yet to yield a clear relationship between the Asperity AE (AAE) and Λ ratio, this is in part due to the complexity of gear tooth contacts. In this paper, a disc rig was used to simulate a simplified gear contact so that the fundamental relationship between AAE and Λ could be investigated more effectively. By varying oil temperature and entrainment speed, a wide spectrum of lubrication conditions was generated. In contrast to other published studies, an independent measurement technique, the contact voltage (CV), was used to verify the amount of interactions, and repeated roughness measurements were used to confirm minimal surface wear. A simple, consistent and precise relationship between AAE amplitude and Λ was identified and defined for changes from full-film to mixed lubrication. Within the mixed lubrication regime, the AAE amplitude increased exponentially as Λ decreased at all speeds tested. It was also observed that an increase in speed always resulted in an increase in AAE amplitude, independently of any changes in Λ . This direct effect of speed was modelled so that the AAE could be predicted for any combination of speed and Λ within the tested envelope. This paper links gear contact tribology and AE with new precision and clearly demonstrates the potential of using AAE as a sensitive monitoring technique for the lubrication condition of gears.

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