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.

Micropitting Fatigue Wear Simulation in Conformal-Contact Under Mixed Elastohydrodynamic Lubrication

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Hang Jia ◽  
Junyang Li ◽  
Jiaxu Wang ◽  
Guo Xiang ◽  
Ke Xiao ◽  
...  
Keyword(s):  
Prediction Model ◽  
Theoretical Calculations ◽  
Normal Load ◽  
Elastohydrodynamic Lubrication ◽  
Dynamic Contact ◽  
Contact Model ◽  
Fatigue Wear ◽  
Cycle Number ◽  
Average Maximum ◽  
Stress Prediction

In this study, a physics-based fatigue wear model is proposed to evaluate the reliability and to predict the life of cumulative micropitting wear for lubricated conformal contacts on rough surfaces. The surface normal load, mean film thickness, and frictional shear traction are simulated by a mixed elastohydrodynamic lubrication (EHL) model for a stress prediction model to calculate the average maximum Hertzian pressure of contact asperities and unit with the statistical contact model and dynamic contact model to obtain the asperity stress cycle number. The wear formula is established through combining a micropitting life prediction model of surface asperities and a mean micropitting damage constant of asperities. The four dominant aspects affecting wear behaviors of the surface contact pairs, working conditions, structure and surface topographies, material properties and lubrication conditions are all taken into account in the model. It is a high-fidelity and comprehensive model that can be used to analyze and optimize the tribological design of rolling–sliding pairs in machinery. The micropitting fatigue wear modeling scheme is validated by comparison of theoretical calculations and available experimental wear data.

Prediction of Leakage Based on the Change of the Surface Topography

2013 ◽  
Vol 712-715 ◽  
pp. 399-402
Author(s):  
Rong Yan Chen ◽  
Gao Liang Peng ◽  
Xin Li
Keyword(s):  
Surface Topography ◽  
Distinct Element ◽  
Fractal Theory ◽  
Contact Model ◽  
Working Process ◽  
Set Up ◽  
Meso Scale

The aim of this paper is to present a method to predict the leakage of the seal dynamically. The surface of the seal in the sealing area is modeled based on fractal theory. In order to simulate the change of the surface topography during the working process, a meso-scale contact model is set up. The simulation is accomplished with the distinct element software, PFC2D. This will be helpful to predict the lifetime of O-ring in mechanical application.

A New Prediction Methodology For Dynamic Contact Pressure Distribution In A Disc Brake

2012 ◽  
Author(s):  
Abd Rahim Abu Bakar ◽  
Mohd Kameil Abdul Hamid ◽  
Huajiang Ouyang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Pressure Distribution ◽  
Surface Topography ◽  
Contact Pressure ◽  
Dynamic Contact ◽  
Element Model ◽  
Disc Brake ◽  
Contact Pressure Distribution ◽  
Static Contact

Taburan tekanan sentuhan dinamik masih lagi tidak dapat diukur secara uji kaji. Ini menjadikan kaedah berangka melalui analisis unsur terhingga merupakan pilihan alternatif yang terbaik bagi tujuan tersebut. Namun begitu, model unsur terhingga yang dibina perlu terlebih dahulu diujisahkan agar hasil ramalan yang diperolehi memuaskan dan realistik. Kertas kerja ini mencadangkan dan menjalankan pengujisahan ke atas model secara tiga peringkat iaitu mengujisahkan aspek kelakuan dinamik pada setiap komponen brek cakera dan juga pemasangan selain daripada pengujisahan tekanan sentuhan statik dengan keputusan daripada pengujian. Model 3-dimensi telah dibina berdasarkan komponen sebenar. Permukaan topografi bahan geseran diambilkira dan dimodelkan dalam model unsur terhingga. Hasil analisis mencatatkan keputusan yang memberangsangkan di mana model menunjukkan persamaan dengan keputusan uji kaji bagi kelakukan dinamik dan juga tekanan sentuhan statik. Setelah model diujisahkan, analisis tekanan sentuhan dinamik dilakukan. Kata kunci: brek cakera, tekanan sentuhan dinamik, topografi permukaan, ujian sentuhan, analisis modal, unsur terhingga The dynamic contact pressure distribution in a disc brake system remains impossible to measure through experimental methods. This makes numerical analysis using the finite element method an indispensable alternative tool to its prediction. However, the finite element model must first be validated through appropriate analyses so that realistic predicted results can be obtained. This paper proposes and carries out a three-stage validation methodology: validating the dynamic aspect of each brake component and the brake assembly using modal testing data and the contact aspect using the experimental results of static contact pressure. A detailed 3-dimensional finite element model of an actual disc brake was developed. Brake pad surface topography is also taken into consideration. Good agreement is achieved between predicted and experimental results both in modal analysis and static contact pressure distributions. Once a validated model was obtained, contact analysis for dynamic condition of the disc brake is performed. Key words: disc brake, dynamic contact pressure, surface topography, contact tests, modal analysis, finite element

Review on Rock Joint Contact Model

2012 ◽  
Vol 170-173 ◽  
pp. 232-236
Author(s):  
Li Fang Zou ◽  
Wei Jie Deng
Keyword(s):  
Interaction Effect ◽  
Rough Surfaces ◽  
Rock Joint ◽  
Contact Problems ◽  
Contact Model ◽  
Normal Loading ◽  
Multi Scale ◽  
Scale Models ◽  
Joint Contact ◽  
Contact Models

The contact of nominally flat rough surfaces can be applied in rock joint contact problems. Statistical, fractal and multi-scale models for surfaces under normal loading are reviewed. The assumptions usually used in those contact models are illustrated. The criteria for distinguishing surfaces which touch elastically from those which touch plastically are analyzed. Moreover, the interaction effect of asperities under loading is discussed.

Modeling and impact analysis on contact characteristic of the compaction roller for composite automated placement

2018 ◽  
Vol 37 (23) ◽  
pp. 1418-1432 ◽  
Author(s):  
Jinxiang Cheng ◽  
Dongbiao Zhao ◽  
Kai Liu ◽  
Yangwei Wang ◽  
Huaiyuan Chen
Keyword(s):  
Impact Analysis ◽  
Dynamic Contact ◽  
Contact Model ◽  
Roller Compaction ◽  
Deformation Model ◽  
Good Precision ◽  
Creep Theory ◽  
Static Contact ◽  
Contact Characteristic ◽  
Automated Placement

Composite automated placement shows great potential for efficient manufacturing of large aviation components. In order to understand the effect of the contact between the compaction roller and the fiber/tape on the layup quality, it is necessary to study the contact characteristic of the compaction roller and the morphological change of the prepreg under the compaction roller. The contact of the compaction roller is divided into the static and dynamic contact. For the static contact, the contact model is simplified to a roller compaction on an elastic body with curved surfaces, and it is developed based on the elastic contact theory. On the contrary, a dynamic contact model is presented by simplifying the contact areas as idealized rectangular elements with identically sized elements. Due to the compaction roller exerting pressure on the prepreg, the morphology of the prepreg will change with different processing parameters. The deformation model of the prepreg is determined as the resin flows through a porous network of fibers by creep theory. A series of experiments had been conducted to verify feasibility and accuracy of the developed models. Results demonstrate that these models have good precision.

Low-Loss Images in a Stem/Tem Microscope

1976 ◽  
Vol 34 ◽  
pp. 496-497 ◽  
Author(s):  
David C. Joy ◽  
Dennis M. Maher
Keyword(s):  
High Resolution ◽  
Surface Topography ◽  
Beam Direction ◽  
Low Loss ◽  
Specimen Holder ◽  
Glancing Angle ◽  
High Resolution Images ◽  
Set Up ◽  
Conventional Manner ◽  
Objective Type

High-resolution images of the surface topography of solid specimens can be obtained using the low-loss technique of Wells. If the specimen is placed inside a lens of the condenser/objective type, then it has been shown that the lens itself can be used to collect and filter the low-loss electrons. Since the probeforming lenses in TEM instruments fitted with scanning attachments are of this type, low-loss imaging should be possible.High-resolution, low-loss images have been obtained in a JEOL JEM 100B fitted with a scanning attachment and a thermal, fieldemission gun. No modifications were made to the instrument, but a wedge-shaped, specimen holder was made to fit the side-entry, goniometer stage. Thus the specimen is oriented initially at a glancing angle of about 30° to the beam direction. The instrument is set up in the conventional manner for STEM operation with all the lenses, including the projector, excited.

The Pressure Drop and Dynamic Contact Angle of Motion of Triple-Lines in Hydrophobic Microchannels

2010 ◽  
Author(s):  
Dongin Yu ◽  
Chiwoong Choi ◽  
Moohwan Kim
Keyword(s):  
Contact Angle ◽  
Pressure Drop ◽  
Liquid Film ◽  
Dynamic Contact Angle ◽  
Triple Line ◽  
Dynamic Contact ◽  
Superficial Velocity ◽  
Channel Diameter ◽  
Fluid Property ◽  
Static Contact

At two-phase flow in microchannels, slug flow regime is different for wettability of surface. A slug in a hydrophilic microchannel has liquid film. However, a slug in a hydrophobic microchannel has no liquid film instead, the slug has triple-lines and makes higher pressure drop due to the motion of the triple-line. In previous researches, pressure drop of triple-line is depended of dynamic contact angle, channel diameter and fluid property. And, dynamic contact angle is depended of static contact angle, superficial velocity and fluid property. In order to understand the pressure drop of motion of triple-lines, pressure drop of slug with triple-lines in case of various diameters (0.546, 0.763, 1.018, 1.555, 2.075 mm), various fluids (D.I.water, D.I.water-1, 5, 10% ethanol mixture) and various superficial velocity (j = 0.01∼0.4 m/s) was measured. Dynamic contact angle was calculated from relation of the pressure drop of slug with triple-lines. Comparing with previous dynamic contact angle correlations, previous correlation underestimated dynamic contact angle in the region of this study. (10−4≤Ca≤10−3, 10−2≤We≤10−1, 68°≤θS≤110°)

scholarly journals Numerical Bifurcation Analysis of a Film Flowing over a Patterned Surface through Enhanced Lubrication Theory

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 405
Author(s):  
Nicola Suzzi ◽  
Giulio Croce
Keyword(s):  
Contact Angle ◽  
Bifurcation Analysis ◽  
Dynamic Contact Angle ◽  
Flow Characteristics ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Inclined Plate ◽  
Lubrication Equation ◽  
Static Contact ◽  
Numerical Bifurcation

The bifurcation analysis of a film falling down an hybrid surface is conducted via the numerical solution of the governing lubrication equation. Instability phenomena, that lead to film breakage and growth of fingers, are induced by multiple contamination spots. Contact angles up to 75∘ are investigated due to the full implementation of the free surface curvature, which replaces the small slope approximation, accurate for film slope lower than 30∘. The dynamic contact angle is first verified with the Hoffman–Voinov–Tanner law in case of a stable film down an inclined plate with uniform surface wettability. Then, contamination spots, characterized by an increased value of the static contact angle, are considered in order to induce film instability and several parametric computations are run, with different film patterns observed. The effects of the flow characteristics and of the hybrid pattern geometry are investigated and the corresponding bifurcation diagram with the number of observed rivulets is built. The long term evolution of induced film instabilities shows a complex behavior: different flow regimes can be observed at the same flow characteristics under slightly different hybrid configurations. This suggest the possibility of controlling the rivulet/film transition via a proper design of the surfaces, thus opening the way for relevant practical application.

Sign in / Sign up

Export Citation Format

Share Document