Two-Dimensional Adaptive-Surface Elasto-Plastic Asperity Contact Model

2006 ◽  
Vol 128 (4) ◽  
pp. 898-903 ◽  
Author(s):  
Tianxiang Liu ◽  
Geng Liu ◽  
Qin Xie ◽  
Q. Jane Wang
Keyword(s):  
Computing Time ◽  
Surface Profile ◽  
Contact Problems ◽  
Contact Model ◽  
Computational Time ◽  
Real Contact Area ◽  
Asperity Contact ◽  
Relative Errors ◽  
Domain Discretization ◽  
Element Free

When contact problems are solved by numerical approaches, a surface profile is usually described by a series of discrete nodes with the same intervals along a coordinate axis. Contact computation based on roughness datum mesh may be time consuming. An adaptive-surface elasto-plastic asperity contact model is presented in this paper. Such a model is developed in order to reduce the computing time by removing the surface nodes that have little influence on the contact behavior of rough surfaces. The nodes to be removed are determined by a prescribed threshold. The adaptive-surface asperity contact model is solved by means of the element-free Galerkin-finite element coupling method because of its flexibility in domain discretization and versatility in node arrangements. The effects of different thresholds on contact pressure distribution, real contact area, and elasto-plastic stress fields in contacting bodies are investigated and discussed. The results show that this model can help reduce about 48% computational time when the relative errors are about 5%.

A Two-Dimensional Adaptive Elasto-Plastic Contact Model of Rough Surfaces

2005 ◽  
Author(s):  
Tianxiang Liu ◽  
Geng Liu ◽  
Qin Xie
Keyword(s):  
Rough Surfaces ◽  
Computing Time ◽  
Surface Profile ◽  
Contact Problems ◽  
Contact Model ◽  
Computational Time ◽  
Real Contact Area ◽  
Asperity Contact ◽  
Pressure Distributions ◽  
Element Free

When contact problems are solved by numerical approaches, the surface profile is usually described by a series of discrete nodes with the same intervals along the coordinate axis. An adaptive-surface-based elasto-plastic asperity contact model is presented in this paper. Such a model is developed in order to reduce the computing time by removing the surface nodes that have little influence on the contact behavior of rough surfaces. The removed nodes are determined by setting a threshold. Thus, the contact problems can be described by fewer surface nodes but have similar results to the ones of the original surface. The adaptive asperity contact model is solved by using the element-free Galerkin-finite element (EFG-FE) coupling method because of its flexibility in domain descritization and versatility in node arrangements. The effects of different thresholds on the contact pressure distributions, real contact area, and the elasto-plastic stress fields in the contacting bodies are investigated and discussed. The results show that the computational time will dramatically reduce to about 50% when the relative error is about 5%.

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.

Contact Simulation of Three-Dimensional Rough Surfaces Using Moving Grid Method

1993 ◽  
Vol 115 (4) ◽  
pp. 597-601 ◽  
Author(s):  
Ning Ren ◽  
Si C. Lee
Keyword(s):  
Rough Surfaces ◽  
Computing Time ◽  
Three Dimensional ◽  
Random Access ◽  
Grid Method ◽  
Contact Problems ◽  
Computational Time ◽  
Moving Grid ◽  
Memory Size ◽  
Surface Profiles

A new method for simulating dry contacts of three-dimensional rough surfaces has been developed. The present work is based upon Moving Grid Method (MGM) which greatly reduces the required computer memory size. One of the major difficulties in simulating contact problems is the huge requirement in computer Random Access Memory (RAM). The total number of nodes (N) to represent a typical three dimensional roughness topography can easily be in the order of tens of thousands. To store the corresponding deformation matrix based on conventional matrix method requires memory size in the order of N2. The computational time necessary to construct such a matrix is also proportional to N2. Thus a reasonable solution for the three dimensional contact problem can be difficult to obtain. In Moving Grid Method, the required storage space for the deformation matrix is reduced to the order of N. The computing time to construct the matrix is also proportional to N. The contact simulation solutions which include the asperity pressure distributions and the corresponding deformed surface profiles were calculated. The digitized surface profiles were used in the simulations. The 3-D results were compared with an existing 2-D model and the comparison showed excellent agreement.

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.

On a model for the prediction of asperity interactions of the coated friction pair

2019 ◽  
Vol 72 (3) ◽  
pp. 449-454 ◽  
Author(s):  
Chunxing Gu ◽  
Shuwen Wang
Keyword(s):  
Optimum Design ◽  
Numerical Experiments ◽  
Rough Surfaces ◽  
Contact Model ◽  
Real Contact Area ◽  
Plastic Behavior ◽  
Asperity Contact ◽  
Content Type ◽  
Contact Behavior ◽  
Elastic Plastic

Purpose Surface coatings have been introduced on the contact surfaces to protect the mechanical parts for a long time. However, in terms of the optimum design of coatings, some key coating parameters are still selected by trial and error. The optimum design of coatings can be conducted by numerical experiments. This paper aims to predict the contact behavior of the coated rough surfaces accurately. One improved asperity contact model for the coated rough surfaces considering the misalignment of asperities would be developed. Design/methodology/approach Incorporating the coated asperity contact model into the improved Greenwood Tripp-based statistical approach, the proposed model can predict the elastic-plastic behaviors of the interacting coated asperities. Findings According to numerical experiments, compared with the coated asperity contact model in which an equivalent rough surface against a plane is assumed, the improved asperity contact model for the coated contacts can account for the effect of permitting misalignment of two rough surfaces. The contacts having the thicker, stiffer and harder coatings result in higher asperity contact pressure and smaller real contact area fraction under the given Stribeck oil film ratio. Originality/value In this paper, one statistical coated asperity contact model for two rough surfaces was developed. The developed model can consider the elastic-plastic behavior of interacting coated asperities. The effects of the coating thickness and its mechanical properties on the contact behavior of the rough surfaces with coatings can be evaluated based on the developed model.

Effective Modeling of Load Applications in Composite Structures - Accuracy, Complexity, Computational Time

2019 ◽  
Vol 809 ◽  
pp. 461-466 ◽  
Author(s):  
Michail Schlosser ◽  
Axel Schumacher ◽  
Klaus Bellendir
Keyword(s):  
Composite Structures ◽  
Contact Point ◽  
Computing Time ◽  
Contact Analysis ◽  
Material Behavior ◽  
Contact Model ◽  
Hertzian Contact ◽  
Computational Time ◽  
Good Representation ◽  
Load Model

The simulation of load application elements requires the modeling of the contact point and a nonlinear analysis. This contact analysis is still time-consuming despite of powerful computers. A reduction of this contact by a simple load model would result in enormous time savings. The Hertzian contact theory provides an analytical approach to the contact problem. However, an isotropic material behavior is assumed, which is problematic especially with fiber reinforced structures. Nevertheless, a suitable load model can be developed for a simplified model of a bolt joint. The edge effects occurring at the edge of the hole are determined using an approximation function (parameterized polynomial approach). The anisotropic material behavior is represented by alternative models or it can also be integrated into the calculation by an extension of Hertzian theory. The different approaches are compared in respect of accuracy, complexity and computing time. For reference and verification of the results, a contact model is created using the FEM software HyperMesh and Optistruct from Altair. Besides the contact model can be used as an aid for creating the load model. Finally, a method is presented, which reduces a contact analysis to a purely linear static structural analysis and thus enables a significantly reduced computing time. The corresponding load model also gives a good representation of reality.

scholarly journals A Cylindrical Contact Model for Two-Dimensional Multiasperity Profiles

2003 ◽  
Author(s):  
John J. Jagodnik ◽  
Sinan Mu¨ftu¨
Keyword(s):  
Three Dimensional ◽  
Local Maximum ◽  
Contact Problems ◽  
Pressure Profile ◽  
Contact Model ◽  
Total Force ◽  
Asperity Contact ◽  
Two Dimensional ◽  
Depth Direction ◽  
Contact Parameters

In practice, multi-asperity contact problems are often solved as two dimensional (2D) plane problems rather than true three dimensional (3D) problems. This is accomplished by assuming that each peak on a 2D scanned profile is the pinnacle of a half sphere. Hertz contact equations are then used to solve for the radius of contact and pressure profile. In reality, the local maximum in the plane may not be the maximum in the unmeasured depth direction, creating inherent errors in the contact model. This error is shown to be significant in contact problems when estimating the area of contact and total contact force over a single asperity. The pressure corrected Sternberg-Turteltaub model is introduced, in which a cylinder is used to model a sphere in a plane. This model is shown to improve the contact area and total force estimates for a range contact parameters.

A New Adaptive-Surface Elastic-Plastic Contact Model of Rough Surfaces: Parameter Correlations

2006 ◽  
Vol 532-533 ◽  
pp. 961-964
Author(s):  
Min Song
Keyword(s):  
Rough Surface ◽  
Root Mean Square ◽  
Rough Surfaces ◽  
Computing Time ◽  
Contact Model ◽  
Asperity Contact ◽  
Mean Square ◽  
Elastic Plastic ◽  
Surface Profiles

Based on an presented adaptive-surface elastic-plastic asperity contact model which can greatly decrease contact computing time and keep the precision loss less than 5%, a series of 2-D rough surface profiles with different roughness and correlative length are numerically generated to investigate how to select the threshold used in this model for different adaptive rough surfaces. The results show that well acceptable precision of the elastic-plastic contact calculation would be derived when the ratio of threshold to root mean square curvature, δ 1.0 10 6mm2 − < × .

scholarly journals Numerical Aspects of Particle-in-Cell Simulations for Plasma-Motion Modeling of Electric Thrusters

Aerospace ◽  
2021 ◽  
Vol 8 (5) ◽  
pp. 138
Author(s):  
Giuseppe Gallo ◽  
Adriano Isoldi ◽  
Dario Del Gatto ◽  
Raffaele Savino ◽  
Amedeo Capozzoli ◽  
...  
Keyword(s):  
Numerical Model ◽  
Computing Time ◽  
Computational Time ◽  
Electric Motors ◽  
Motion Modeling ◽  
Particle In Cell ◽  
Computing Platform ◽  
Hall Effect Thruster ◽  
Set Up ◽  
Pic Code

The present work is focused on a detailed description of an in-house, particle-in-cell code developed by the authors, whose main aim is to perform highly accurate plasma simulations on an off-the-shelf computing platform in a relatively short computational time, despite the large number of macro-particles employed in the computation. A smart strategy to set up the code is proposed, and in particular, the parallel calculation in GPU is explored as a possible solution for the reduction in computing time. An application on a Hall-effect thruster is shown to validate the PIC numerical model and to highlight the strengths of introducing highly accurate schemes for the electric field interpolation and the macroparticle trajectory integration in the time. A further application on a helicon double-layer thruster is presented, in which the particle-in-cell (PIC) code is used as a fast tool to analyze the performance of these specific electric motors.

scholarly journals The time machine: a simulation approach for stochastic trees

2011 ◽  
Vol 467 (2132) ◽  
pp. 2350-2368 ◽  
Author(s):  
Ajay Jasra ◽  
Maria De Iorio ◽  
Marc Chadeau-Hyam
Keyword(s):  
Variance Reduction ◽  
Sequential Monte Carlo ◽  
Likelihood Function ◽  
Computing Time ◽  
Point Of View ◽  
Computational Time ◽  
Recent Common Ancestor ◽  
Theoretical Point ◽  
Monte Carlo Techniques ◽  
Most Recent Common Ancestor

In this paper, we consider a simulation technique for stochastic trees. One of the most important areas in computational genetics is the calculation and subsequent maximization of the likelihood function associated with such models. This typically consists of using importance sampling and sequential Monte Carlo techniques. The approach proceeds by simulating the tree, backward in time from observed data, to a most recent common ancestor. However, in many cases, the computational time and variance of estimators are often too high to make standard approaches useful. In this paper, we propose to stop the simulation, subsequently yielding biased estimates of the likelihood surface. The bias is investigated from a theoretical point of view. Results from simulation studies are also given to investigate the balance between loss of accuracy, saving in computing time and variance reduction.

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