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

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.

Effects of Lattice Orientation and Size on Molecular Asperity Contact Models

2009 ◽  
Author(s):  
J. Robert Polchow ◽  
Wei Huang ◽  
Robert L. Jackson
Keyword(s):  
Contact Mechanics ◽  
Molecular Model ◽  
Rough Surfaces ◽  
Minimum Size ◽  
Small Scale ◽  
Asperity Contact ◽  
Lattice Orientation ◽  
Noticeable Effect ◽  
Contact Models ◽  
Number Of Particles

Surface asperities can range widely in size. Therefore it is important to characterize the effect of size and scale on the contact mechanics. This work presents a molecular model of asperity contact in order to characterize small scale asperity contact. The effects of lattice orientation and radius (number of particles) are examined. It appears that lattice orientation has a noticeable effect, but nominally may not be important in the contact of asperities and rough surfaces. The size appears to be important until a certain minimum size is achieved.

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.

scholarly journals A Review of Elastic–Plastic Contact Mechanics

2017 ◽  
Vol 69 (6) ◽  
Author(s):  
Hamid Ghaednia ◽  
Xianzhang Wang ◽  
Swarna Saha ◽  
Yang Xu ◽  
Aman Sharma ◽  
...  
Keyword(s):  
State Of The Art ◽  
Asperity Contact ◽  
Elastic Plastic ◽  
Single Asperity ◽  
Current State ◽  
Metallic Contacts ◽  
Contact Models ◽  
Rough Surface Contact ◽  
Elastic And Plastic Deformation ◽  
Very High

In typical metallic contacts, stresses are very high and result in yielding of the material. Therefore, the study of contacts which include simultaneous elastic and plastic deformation is of critical importance. This work reviews the current state-of-the-art in the modeling of single asperity elastic–plastic contact and, in some instances, makes comparisons to original findings of the authors. Several different geometries are considered, including cylindrical, spherical, sinusoidal or wavy, and axisymmetric sinusoidal. As evidenced by the reviewed literature, it is clear that the average pressure during heavily loaded elastic–plastic contact is not governed by the conventional hardness to yield strength ratio of approximately three, but rather varies according to the boundary conditions and deformed geometry. For spherical contact, the differences between flattening and indentation contacts are also reviewed. In addition, this paper summarizes work on tangentially loaded contacts up to the initiation of sliding. As discussed briefly, the single asperity contact models can be incorporated into existing rough surface contact model frameworks. Depending on the size of a contact, the material properties can also effectively change, and this topic is introduced as well. In the concluding discussion, an argument is made for the value of studying hardening and other failure mechanisms, such as fracture as well as the influence of adhesion on elastic–plastic contact.

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.

Transient Friction Effects Due to Variable Normal Load in a Multi-Scale Asperity-Creep Friction Model

2010 ◽  
Author(s):  
Andreas Goedecke ◽  
Randolf Mock
Keyword(s):  
Dwell Time ◽  
Normal Force ◽  
Normal Load ◽  
Transient Behavior ◽  
Friction Model ◽  
Creep Model ◽  
Small Scale ◽  
Asperity Contact ◽  
Multi Scale ◽  
Contact Models

The study of multi-scale and fractal contact geometries holds many insights into the nature of surface contact. As a common feature of most fractal contact models, the presence of small-scale, plastically loaded asperities has emerged. The latter are, due to their loading close to the yield strength of the material, subject to creep deformation which is often held responsible for transient friction effect like dwell time- or velocity-dependent friction. In this paper, the transient behavior of friction under varying normal force will be studied in the framework of a multi-scale contact model with fractal input parameters. An advanced asperity creep model from previous research is used, yielding the time-dependent creep enlargement of the asperity contact area in response to arbitrary load transients.

scholarly journals Validation of statistic and deterministic asperity contact models using experimental Stribeck data

2021 ◽  
pp. 107329
Author(s):  
Michael Maier ◽  
Michael Pusterhofer ◽  
Florian Summer ◽  
Florian Grün
Keyword(s):  
Asperity Contact ◽  
Contact Models

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.

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