A Multi-Scale Model for Contact Between Rough Surfaces

2005 ◽  
Author(s):  
Robert L. Jackson ◽  
Jeffrey L. Streator
Keyword(s):  
Scale Effects ◽  
Rough Surfaces ◽  
Measurement Techniques ◽  
Surface Profile ◽  
Scale Model ◽  
Real Surface ◽  
Normal Contact ◽  
Multi Scale ◽  
Fractal Analyses ◽  
Deformation Mechanics

This work describes a non-statistical multi-scale model of the normal contact between rough surfaces. The model produces predictions for contact area as a function of contact load, and is compared to the traditional Greenwood and Williamson (GW) and Majumdar and Bhushan (MB) rough surface contact models, which represent single-scale and fractal analyses, respectively. The current model incorporates the effect of asperity deformations at multiple scales into a simple framework for modeling the contact between nominally flat rough surfaces. Similar to the “protuberance upon protuberance” theory proposed by Archard, the model considers the effect of having smaller asperities located on top of larger asperities in repeated fashion with increasing detail down to the limits of current measurement techniques. The parameters describing the surface topography (areal asperity density and asperity radius) are calculated from an FFT performed of the surface profile. Thus, the model considers multi-scale effects, which fractal methods have addressed, while attempting to more accurately incorporate the deformation mechanics into the solution. After the FFT of a real surface is calculated, the computational resources needed for the method are very small. Perhaps surprisingly, the trends produced by this non-statistical multi-scale model are quite similar to those arising from the GW and MB models.

Prediction of Contact Area and Frictional Behaviour of Rubber on Rigid Rough Surfaces

2014 ◽  
Author(s):  
Hagen Lind ◽  
Matthias Wangenheim
Keyword(s):  
Contact Area ◽  
Surface Texture ◽  
Rough Surfaces ◽  
Scale Model ◽  
Real Contact Area ◽  
Contact Friction ◽  
Sliding Velocity ◽  
Normal Contact ◽  
Multi Scale ◽  
Frictional Behaviour

In the tire-road contact friction depends on several influencing variables (e.g. surface texture, real contact area, sliding velocity, normal contact pressure, temperature, tread block geometry, compound and on the existence of a lubrication film). A multi-scale model for prediction of contact area and frictional behaviour of rubber on rigid rough surfaces at different length scales is presented. Within this publication the multi-scale approach is checked regarding convergence. By means of the model influencing parameters like sliding velocity, compound and surface texture on friction and contact area will be investigated.

Critical Conditions for Liquid Mediated Collapse of Two-Dimensional Rough Surfaces

2007 ◽  
Author(s):  
Jeffrey L. Streator ◽  
Robert L. Jackson
Keyword(s):  
Liquid Droplet ◽  
Rough Surfaces ◽  
Full Range ◽  
Surface Profile ◽  
Adhesive Force ◽  
Scale Model ◽  
Critical Conditions ◽  
Liquid Volume ◽  
Small Scale ◽  
Unit Depth

Small-scale devices are particularly vulnerable to adverse effects of adhesion because of large surface-area-to-volume ratios. Additionally, small gaps can be easily bridged at high humidity or when there are other contaminant liquids present. The bridging of a portion of the interface by a liquid droplet of given volume, tends to pull surfaces in closer proximity due to the sub-ambient pressures that arise. In turn, regions spanned by the bridge will increase in size and lead to a greater adhesive force. In the present work we develop a model for these effects in the presence of surface roughness. The influence of asperities on the surface is treated by means of a recently-developed multi-scale model that considers the full range of wavelengths comprising the surface profile. In the simulations, two nominally flat rough surfaces with profiles that vary only in one direction are brought together under a prescribed load. A liquid bridge of given volume (per unit depth) is then introduced into the contact, assuming an initial areal coverage. The interface configuration is then iterated until one is found that satisfies the equations of elasticity and capillarity for a given liquid volume. As a result of the simulation, critical values are found for combinations of parameters that delineate stable and unstable conditions.

scholarly journals Multi-scale atmospheric environment modelling for urban areas

2009 ◽  
Vol 3 (1) ◽  
pp. 53-57 ◽  
Author(s):  
A. A. Baklanov ◽  
R. B. Nuterman
Keyword(s):  
Urban Areas ◽  
Scale Effects ◽  
Urban Setting ◽  
Atmospheric Environment ◽  
Scale Model ◽  
Limited Area ◽  
Nested Models ◽  
Micro Scale ◽  
Multi Scale ◽  
Meso Scale

Abstract. Modern supercomputers allow realising multi-scale systems for assessment and forecasting of urban meteorology, air pollution and emergency preparedness and considering nesting with obstacle-resolved models. A multi-scale modelling system with downscaling from regional to city-scale with the Environment – HIgh Resolution Limited Area Model (Enviro-HIRLAM) and to micro-scale with the obstacle-resolved Micro-scale Model for Urban Environment (M2UE) is suggested and demonstrated. The M2UE validation results versus the Mock Urban Setting Trial (MUST) experiment indicate satisfactory quality of the model. Necessary conditions for the choice of nested models, building descriptions, areas and resolutions of nested models are analysed. Two-way nesting (up- and down-scaling), when scale effects both directions (from the meso-scale on the micro-scale and from the micro-scale on the meso-scale), is also discussed.

Numerical Simulation of Scale Effects in Contacting Rough Surfaces

2008 ◽  
Author(s):  
Jeffrey L. Streator
Keyword(s):  
Numerical Simulation ◽  
Surface Topography ◽  
Scale Effects ◽  
Surface Profile ◽  
Length Scales ◽  
Multi Scale ◽  
Multiple Length Scales ◽  
Asperity Contacts ◽  
Contact Models ◽  
Simulated Surface

It is well known that surface topography is composed of multiple length scales. Yet it remains a challenge to ascertain how the various length scales affect the contact area and contact stresses. Several micro-contact models exist in the literature that seek to account for the multi-scale nature of surface topography through fractal or spectral descriptions. A limitation of most such micro-contact models is that they neglect the interaction between asperity contacts. In the current work, a deterministic numerical simulation of contact is performed on the contact between a rigid flat and a rough, elastic surface whose heights vary in a single dimension (i.e., y(x)). A simulated surface profile is created and then “sampled” at several resolutions to create a set of related profiles of various levels of refinement. Contact is investigated with each of the simulated surfaces to gain insight as to the role of various length scales.

A Flexible Multi-Scale Two-Dimensional Model for Calculating the Radial Heat Transfer in Grooved Heat Pipes

2008 ◽  
Author(s):  
Se´verine Rossomme ◽  
Ce´cile Goffaux ◽  
Koen Hillewaert ◽  
Pierre Colinet
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Scale Effects ◽  
Saturation Temperature ◽  
Apparent Contact Angle ◽  
Scale Model ◽  
Small Scale ◽  
Interface Temperature ◽  
Multi Scale ◽  
Radial Heat

This paper describes a multi-scale model for evaluating the radial heat transfer within a grooved heat pipe evaporator. The model is composed of two parts, macroscopic and microscopic, which cannot be decoupled from each other. In the macroscopic part, we solve the heat conduction problem in the solid and in the liquid phases, thanks to a finite-element method allowing high flexibility in the definition of the groove geometry. In order to avoid the classical singularity problem at the contact line (where the liquid-vapor interface meets the groove wall), in addition to taking the solid thermal conductivity into account, we do not impose the saturation temperature but a mixed condition along the interface. We show in particular that the interface temperature equals the saturation temperature (at given vapor pressure), except in the microscopic region where it increases and reaches the solid temperature. In this microscopic zone, a classical lubrication-type theory allows to determine the apparent contact angle, taking into account the influence of small-scale effects, such as the variation of the saturation temperature with the disjoining pressure and with the meniscus curvature. In particular, analytical relationships and correlations are presented for the apparent contact angle, which allow an efficient coupling between macroscopic and microscopic scales. In this paper, attention is devoted to the numerical treatment of both regions, their coupling, and the influence of the macroscopic heat flux and local small-scale effects on the distribution of temperature in the groove.

A multi-scale model for contact between rough surfaces

Wear ◽  
2006 ◽  
Vol 261 (11-12) ◽  
pp. 1337-1347 ◽  
Author(s):  
Robert L. Jackson ◽  
Jeffrey L. Streator
Keyword(s):  
Rough Surfaces ◽  
Scale Model ◽  
Multi Scale

Three-dimensional Reconstruction of Microscopic Image Based on Multi-ST Algorithm

2020 ◽  
Vol 64 (2) ◽  
pp. 20506-1-20506-7
Author(s):  
Min Zhu ◽  
Rongfu Zhang ◽  
Pei Ma ◽  
Xuedian Zhang ◽  
Qi Guo
Keyword(s):  
3D Reconstruction ◽  
Three Dimensional ◽  
Scale Model ◽  
Microscopic Image ◽  
Multi Scale ◽  
Gaussian Pyramid ◽  
Cost Aggregation ◽  
Dimensional Reconstruction ◽  
Image Pairs ◽  
Accurate Matching

Abstract Three-dimensional (3D) reconstruction is extensively used in microscopic applications. Reducing excessive error points and achieving accurate matching of weak texture regions have been the classical challenges for 3D microscopic vision. A Multi-ST algorithm was proposed to improve matching accuracy. The process is performed in two main stages: scaled microscopic images and regularized cost aggregation. First, microscopic image pairs with different scales were extracted according to the Gaussian pyramid criterion. Second, a novel cost aggregation approach based on the regularized multi-scale model was implemented into all scales to obtain the final cost. To evaluate the performances of the proposed Multi-ST algorithm and compare different algorithms, seven groups of images from the Middlebury dataset and four groups of experimental images obtained by a binocular microscopic system were analyzed. Disparity maps and reconstruction maps generated by the proposed approach contained more information and fewer outliers or artifacts. Furthermore, 3D reconstruction of the plug gauges using the Multi-ST algorithm showed that the error was less than 0.025 mm.

Effects of parametric uncertainty on multi-scale model predictions of shock response of a pressed energetic material

2019 ◽  
Vol 125 (23) ◽  
pp. 235104 ◽  
Author(s):  
Sangyup Lee ◽  
Oishik Sen ◽  
Nirmal Kumar Rai ◽  
Nicholas J. Gaul ◽  
K. K. Choi ◽  
...  
Keyword(s):  
Energetic Material ◽  
Parametric Uncertainty ◽  
Scale Model ◽  
Multi Scale ◽  
Model Predictions ◽  
Shock Response

scholarly journals The Winter Habitat Selection of Red Deer (Cervus elaphus) Based on a Multi-Scale Model

Animals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2454
Author(s):  
Yue Sun ◽  
Yanze Yu ◽  
Jinhao Guo ◽  
Minghai Zhang
Keyword(s):  
Habitat Selection ◽  
Environmental Factors ◽  
Cervus Elaphus ◽  
Red Deer ◽  
Scale Model ◽  
Winter Habitat ◽  
Multi Scale ◽  
Optimal Scale ◽  
Scale Models ◽  
Selection Of

Single-scale frameworks are often used to analyze the habitat selections of species. Research on habitat selection can be significantly improved using multi-scale models that enable greater in-depth analyses of the scale dependence between species and specific environmental factors. In this study, the winter habitat selection of red deer in the Gogostaihanwula Nature Reserve, Inner Mongolia, was studied using a multi-scale model. Each selected covariate was included in multi-scale models at their “characteristic scale”, and we used an all subsets approach and model selection framework to assess habitat selection. The results showed that: (1) Univariate logistic regression analysis showed that the response scale of red deer to environmental factors was different among different covariate. The optimal scale of the single covariate was 800–3200 m, slope (SLP), altitude (ELE), and ratio of deciduous broad-leaved forests were 800 m in large scale, except that the farmland ratio was 200 m in fine scale. The optimal scale of road density and grassland ratio is both 1600 m, and the optimal scale of net forest production capacity is 3200 m; (2) distance to forest edges, distance to cement roads, distance to villages, altitude, distance to all road, and slope of the region were the most important factors affecting winter habitat selection. The outcomes of this study indicate that future studies on the effectiveness of habitat selections will benefit from multi-scale models. In addition to increasing interpretive and predictive capabilities, multi-scale habitat selection models enhance our understanding of how species respond to their environments and contribute to the formulation of effective conservation and management strategies for ungulata.

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