scholarly journals Numerical prediction of the frictional losses in sliding bearings during start-stop operation

Friction ◽  
2020 ◽  
Author(s):  
Florian König ◽  
Christopher Sous ◽  
Georg Jacobs
Keyword(s):  
Detailed Comparison ◽  
Numerical Prediction ◽  
Contact Model ◽  
Engineering Practice ◽  
Asperity Contact ◽  
Sliding Bearings ◽  
Actual Distribution ◽  
Automotive Engine ◽  
Frictional Losses ◽  
Contact Models

AbstractWith the increased use of automotive engine start-stop systems, the numerical prediction and reduction of frictional losses in sliding bearings during starting and stopping procedures has become an important issue. In engineering practice, numerical simulations of sliding bearings in automotive engines are performed with statistical asperity contact models with empirical values for the necessary surface parameters. The aim of this study is to elucidate the applicability of these approaches for the prediction of friction in sliding bearings subjected to start-stop operation. For this purpose, the friction performance of sliding bearings was investigated in experiments on a test rig and in transient mixed elasto-hydrodynamic simulations in a multi-body simulation environment (mixed-EHL/MBS). In mixed-EHL/MBS, the extended Reynold’s equation with flow factors according to Patir and Cheng has been combined on the one hand with the statistical asperity contact model according to Greenwood and Tripp and on the other hand with the deterministic asperity contact model according to Herbst. The detailed comparison of simulation and experimental results clarifies that the application of statistical asperity contact models with empirical values of the necessary inputs leads to large deviations between experiment and simulation. The actual distribution and position of surface roughness, as used in deterministic contact modelling, is necessary for a reliable prediction of the frictional losses in sliding bearings during start-stop operation.

Comparative Contact Analysis Study of Finite Element Method Based Deterministic, Simplified Multi-Asperity and Modified Statistical Contact Models

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
A. Megalingam ◽  
M. M. Mayuram
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Rough Surface ◽  
Contact Area ◽  
Model Analysis ◽  
Contact Model ◽  
Contact Load ◽  
Asperity Contact ◽  
Single Asperity ◽  
Contact Models

The study of the contact stresses generated when two surfaces are in contact plays a significant role in understanding the tribology of contact pairs. Most of the present contact models are based on the statistical treatment of the single asperity contact model. For a clear understanding about the elastic-plastic behavior of two rough surfaces in contact, comparative study involving the deterministic contact model, simplified multi-asperity contact model, and modified statistical model are undertaken. In deterministic contact model analysis, a three dimensional deformable rough surface pressed against a rigid flat surface is carried out using the finite element method in steps. A simplified multi-asperity contact model is developed using actual summit radii deduced from the rough surface, applying single asperity contact model results. The resultant contact parameters like contact load, contact area, and contact pressure are compared. The asperity interaction noticed in the deterministic contact model analysis leads to wide disparity in the results. Observing the elastic-plastic transition of the summits and the sharing of contact load and contact area among the summits, modifications are employed in single asperity statistical contact model approaches in the form of a correction factor arising from asperity interaction to reduce the variations. Consequently, the modified statistical contact model and simplified multi-asperity contact model based on actual summit radius results show improved agreement with the deterministic contact model results.

Stratified Revised Asperity Contact Model for Worn Surfaces

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Songtao Hu ◽  
Noel Brunetiere ◽  
Weifeng Huang ◽  
Xiangfeng Liu ◽  
Yuming Wang
Keyword(s):  
Deterministic Model ◽  
Contact Problems ◽  
Contact Model ◽  
Asperity Contact ◽  
Knee Point ◽  
Gaussian Representation ◽  
Contact Models ◽  
Large Roughness ◽  
Gaussian Surface ◽  
Worn Surfaces

Segmented bi-Gaussian stratified elastic asperity contact model of Leefe (1998, “‘Bi-Gaussian’ Representation of Worn Surface Topography in Elastic Contact Problems,” Tribol. Ser., 34, pp. 281–290), which suits for worn surfaces, has been improved. It still exhibits two drawbacks: (1) the arbitrary assumption of the probability density function (PDF) consisting of two component PDFs intersecting at a knee-point, violating the unity-area demand and (2) the preference for large roughness-scale part of the surface, leading to an error on the characterization of small roughness-scale part. A continuous bi-Gaussian stratified elastic asperity contact model is proposed based on a surface combination theory and a continuous separation method. The two stratified contact models are applied to a simulated pure bi-Gaussian surface and four real worn surfaces. The results show that the modified segmented and the continuous stratified contact models are both validated by a deterministic model with better accuracy for the continuous one.

A FEM Based Multiple Asperity Deterministic Contact Model

2009 ◽  
Author(s):  
A. Megalingam ◽  
M. M. Mayuram
Keyword(s):  
Friction And Wear ◽  
Statistical Approach ◽  
Present Model ◽  
Contact Model ◽  
Real Contact Area ◽  
Clear Understanding ◽  
Asperity Contact ◽  
Single Asperity ◽  
Contact Models ◽  
Single Asperity Contact

Knowledge of contact stresses generated when two surfaces are in contact play a significant role in understanding most mechanisms of friction and wear. Most of present contact models are based on the Greenwood-Williamson (GW) single asperity contact model and a statistical approach is adopted to calculate the real contact area for the entire surface based on the assumption that all the summits have uniform radius of curvatures and their heights vary randomly. But in real cases, the asperity radii vary. For a clear understanding about those aspects, a multiple asperity contact model, based on 3-D rough surface generated is analyzed using a commercial FEM package. Salient aspects of the present model are presented here and results are compared with a single asperity contact model.

scholarly journals The effect of sampling interval on the predictions of an asperity contact model of two-process surfaces

2017 ◽  
Vol 65 (3) ◽  
pp. 391-398 ◽  
Author(s):  
P. Pawlus ◽  
R. Reizer ◽  
M. Wieczorowski ◽  
W. Żelasko
Keyword(s):  
Surface Region ◽  
Sampling Interval ◽  
Plasticity Index ◽  
Contact Model ◽  
Asperity Contact ◽  
Normal Contact ◽  
Method Of Calculation ◽  
Surface Separation ◽  
Sampling Intervals ◽  
Flat Steel

AbstractContact of random machined two-process steel textures with a smooth, flat steel surface is discussed in this paper. Two-process surfaces were machined by vapour blasting followed by lapping. An elastic-plastic contact model was applied, assuming distributed radius of asperities. Calculation procedures allowed the mean surface separation, contact pressure, and area fraction to be computed as functions of sampling intervals. Parameters characterizing the summits important in contact mechanics were calculated for different sampling intervals. Plasticity index of two-process textures was calculated using the modified procedure. It was found that the influence of sampling interval on normal contact depended on the rough surface ability to plastic deformation. The use of a traditional method of calculation overestimated the plasticity index. Peaks from plateau surface region governed contact characteristics of two-process surfaces.

Investigation of the Influence of Different Asperity Contact Models on the Elastohydrodynamic Analysis of a Conrod Small-End/Piston Pin Coupling

2018 ◽  
Vol 11 (6) ◽  
pp. 919-934 ◽  
Author(s):  
Andrea Ferretti ◽  
Matteo Giacopini ◽  
Luca Mastrandrea ◽  
Daniele Dini
Keyword(s):  
Asperity Contact ◽  
Contact Models

A complete elastic-plastic spherical asperity contact model with the effect of isotropic strain hardening

2020 ◽  
pp. 135065012092989 ◽  
Author(s):  
A Megalingam ◽  
KS Hanumanth Ramji
Keyword(s):  
Strain Hardening ◽  
Rough Surface ◽  
Contact Area ◽  
Poisson’S Ratio ◽  
Combined Effect ◽  
Contact Model ◽  
Poisson's Ratio ◽  
Contact Load ◽  
Asperity Contact ◽  
Strain Hardening Rate

Understanding the deformation behavior of rough surface contacts is essential to minimise the tribological consequences of contacts. Mostly, statistical, deterministic and fractal approaches are adopted to explore the contact of rough surfaces. In statistical approach, a single asperity contact model is developed and extended to the whole surface. In the present work, a deformable spherical asperity contact with a rigid flat is modeled and analysed by accounting the combined effect of Young’s modulus, Poisson’s ratio, yield strength and isotropic strain hardening rate using finite element method. The results reveal that the elastic, elastoplastic and plastic contact states are highly influenced by E/Y ratio and strain hardening rate followed by Poisson’s ratio. The dimensionless contact radius is an inadequate parameter to explore the combined effect of material properties. For all E/Y ratio and Poisson’s ratio, as the strain hardening rate increases, the dimensionless contact area decreases for the same dimensionless contact load at elastoplastic and fully plastic contact states. As the strain hardening rate increases, the fully plastic contact state is reached at low dimensionless interference compared to elastic perfectly plastic materials for all E/Y ratio and Poisson’s ratio. For a common elastic-plastic material, empirical relations are developed to calculate the contact load and contact area appropriately with E/Y ratio, Poisson’s ratio and interference ratio as input variables. It can be utilised to study the interaction of rough surface contacts for most of the practical materials.

scholarly journals Influence of the Mesoscopic Viscoelastic Contact Model on Characterizing the Rheological Behavior of Asphalt Concrete in the DEM Simulation

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Jiaolong Ren ◽  
Zhe Liu ◽  
Jinshun Xue ◽  
Yinshan Xu
Keyword(s):  
Phase Angle ◽  
Rheological Behavior ◽  
Asphalt Concrete ◽  
Low Temperatures ◽  
Material Behavior ◽  
Contact Model ◽  
Contact Models ◽  
Heterogeneous Microstructures ◽  
Study Laboratory ◽  
Viscoelastic Contact

The numerical simulation based on the discrete element method (DEM) is popular to analyze the material behavior of asphalt concrete in recent years because of the advantage of the DEM in characterizing the heterogeneous microstructures. As a type of viscoelastic material, the rheological behavior of asphalt concrete is represented depending on the mesoscopic viscoelastic contact model between two particles in a contact in DEM simulations. However, what is missing in the existing literature studies is analysis of the influence of the mesoscopic viscoelastic contact models. Hence, the existing mesoscopic viscoelastic contact models are employed to build different types of DEM numerical samples of asphalt concrete in this study. Laboratory tests and the corresponding numerical tests at different temperatures and frequencies are implemented to investigate the difference in simulation precision in the case of using different mesoscopic viscoelastic contact models via the rheological index of dynamic modulus and phase angle. The results show the following: (1) the mesoscopic generalized Maxwell contact model provides the best simulation precision at low temperatures; (2) the mesoscopic generalized Kelvin contact model shows an improved precision at high temperatures; and (3) although the mesoscopic Burgers contact model has the simplest mathematical structure, the simulation precisions are obviously lower than those of the other two contact models, particularly when simulating the phase angle at low temperatures and frequencies. The results will be beneficial to select the appropriate mesoscopic contact model for the DEM modeling of asphalt concrete according to the loading conditions.

A Dynamic Contact Model of Rough Surfaces Based on the Microscopic Contact Analysis of Asperities

2013 ◽  
Vol 785-786 ◽  
pp. 1208-1211
Author(s):  
Yan Qing Tan ◽  
Lian Hong Zhang ◽  
Ya Hui Hu
Keyword(s):  
Surface Topography ◽  
Rough Surfaces ◽  
Dynamic Contact ◽  
Contact Model ◽  
Fatigue Wear ◽  
Contact Parameter ◽  
Wear Process ◽  
Static Contact ◽  
Contact Models ◽  
Set Up

Dynamic contact model of rough surfaces can provide the theoretical basis for analyzing the microscopic damage of surfaces in wear process and constructing the analytical wear model to predict wear. A dynamic contact model of sliding rough surfaces is innovatively constructed based on the characterization of the contact asperities on rough surfaces in this paper. Firstly, an asperity model of rough surface is set up according to the surface topography parameters and the static contact parameters is evaluated in the light of statistics contact theory; Then the contact characteristic of surface topography in sliding is analyzed and a series of equivalent contact models are proposed; Finally, the dynamic contact model of rough surfaces is established and from which the dynamic contact parameter of rough surfaces is formulated. The dynamic contact model can be further improved to analyze the friction fatigue wear of sliding pairs and provide reference for tribology design of mechanical surfaces.

scholarly journals The Effect of the Contact Model on the Design of Mechanical Systems

2012 ◽  
Author(s):  
M. R. Brake ◽  
D. S. Aragon ◽  
D. J. VanGoethem ◽  
H. Sumali
Keyword(s):  
Constant Coefficient ◽  
Degrees Of Freedom ◽  
Mechanical Systems ◽  
Constitutive Models ◽  
Coefficient Of Restitution ◽  
Rigid Body Dynamics ◽  
Contact Model ◽  
Elastic Plastic ◽  
Contact Models ◽  
The Impact

Impact is a wide-spread phenomenon in mechanical systems that can have a significant effect on the system’s dynamics, stability, wear, and damage. The simulation of impact in complex, mechanical systems, however, is often too computationally intensive for high fidelity finite element analyses to be useful as design tools. As a result, rigid body dynamics and reduced order model simulations are often used, with the impact events modeled by ad hoc methods such as a constant coefficient of restitution or a penalty stiffness. The consequences of the choice of contact model are studied in this paper for a representative multiple-degrees of freedom mechanical system. Four contact models are considered in the analysis: a constant coefficient of restitution model, two similar elastic-plastic constitutive models, and one dissimilar elastic-plastic constitutive model. The predictions of wear, mechanical failure, and stability are assessed for each of the contact models, and the subsequent effect on the system design is investigated. These results emphasize the importance of choosing a realistic contact model when simulations are being used to drive the design of a system.

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