Influence of Surface Parameters on the Elastoplastic Contact Behavior of Fractal-Regular Surfaces

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
K. Willner
Keyword(s):  
Three Dimensional ◽  
Atomic Scale ◽  
Normal Contact ◽  
Surface Parameters ◽  
Fractal Surfaces ◽  
Minor Influence ◽  
Dimensionless Ratio ◽  
Transition Length ◽  
Geometric Surface ◽  
Height Data

In a recent paper (2004, “Elasto-Plastic Normal Contact of Three-Dimensional Fractal Surfaces Using Halfspace Theory,” J. Tribol., 126, pp. 28–33) the author developed a halfspace model for the elasto-plastic normal contact of rough surfaces. This model is now used to study the influence of intrinsic surface parameters on constitutive contact laws, such as load-gap relation and load-area relation, for a specific type of surface topography known as fractal-regular surfaces. Numerical investigations show that the fractal dimension has only minor influence on the load-gap relationship, which is mostly determined by the dimensionless ratio between the transition length and the rms values of the height data. Due to the fractal nature of the surfaces at the small wavelength limit, initial deformation will always be in the plastic range. The load-area relation becomes then completely independent of the geometric surface parameters and is determined by material properties alone, at least if the predicted plastic deformation occurs at a length scale larger than the atomic scale.

Elasto-Plastic Normal Contact of Three-Dimensional Fractal Surfaces Using Halfspace Theory

2004 ◽  
Vol 126 (1) ◽  
pp. 28-33 ◽  
Author(s):  
K. Willner
Keyword(s):  
Fractal Dimension ◽  
Three Dimensional ◽  
Contact Problems ◽  
Plastic Range ◽  
Elastic Halfspace ◽  
Normal Contact ◽  
Simple Modification ◽  
Surface Parameters ◽  
Fractal Surfaces ◽  
Approximative Solution

The elasto-plastic normal contact of fractal surfaces is investigated. To study the influence of several surface parameters like fractal dimension and resolution, the surfaces are numerically generated using a special form of the structure function which is motivated by measurements of real rough surfaces. The contact simulation uses an iterative elastic halfspace solution based on a variational principle. A simple modification allows also the approximative solution of elasto-plastic contact problems. The influence of different surface parameters is studied with respect to the load-area relationship and the load-gap relationship. The simulations show that for realistic surface parameters the deformation is always in the plastic range.

Tire Modeling by Finite Elements

1992 ◽  
Vol 20 (1) ◽  
pp. 33-56 ◽  
Author(s):  
L. O. Faria ◽  
J. T. Oden ◽  
B. Yavari ◽  
W. W. Tworzydlo ◽  
J. M. Bass ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Rolling Contact ◽  
Test Problems ◽  
State Behavior ◽  
Normal Contact ◽  
New Developments ◽  
Applied Torque ◽  
Dimensional Finite Element ◽  
Tire Modeling ◽  
Three Dimensional Finite Element

Abstract Recent advances in the development of a general three-dimensional finite element methodology for modeling large deformation steady state behavior of tire structures is presented. The new developments outlined here include the extension of the material modeling capabilities to include viscoelastic materials and a generalization of the formulation of the rolling contact problem to include special nonlinear constraints. These constraints include normal contact load, applied torque, and constant pressure-volume. Several new test problems and examples of tire analysis are presented.

scholarly journals Porous Characteristics of Three-Dimensional Disordered Graphene Networks

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 127
Author(s):  
YongChao Wang ◽  
YinBo Zhu ◽  
HengAn Wu
Keyword(s):  
Pore Size ◽  
Low Temperatures ◽  
Gas Adsorption ◽  
Three Dimensional ◽  
Md Simulations ◽  
Structural Features ◽  
Atomic Scale ◽  
Critical Factors ◽  
Chlorination Process ◽  
Porous Morphology

The porous characteristics of disordered carbons are critical factors to their performance on hydrogen storage and electrochemical capacitors. Even though the porous information can be estimated indirectly by gas adsorption experiments, it is still hard to directly characterize the porous morphology considering the complex 3D connectivity. To this end, we construct full-atom disordered graphene networks (DGNs) by mimicking the chlorination process of carbide-derived carbons using annealing-MD simulations, which could model the structure of disordered carbons at the atomic scale. The porous characteristics, including pore volume, pore size distribution (PSD), and specific surface area (SSA), were then computed from the coordinates of carbon atoms. From the evolution of structural features, pores grow dramatically during the formation of polyaromatic fragments and sequent disordered framework. Then structure is further graphitized while the PSD shows little change. For the obtained DGNs, the porosity, pore size, and SSA increase with decreasing density. Furthermore, SSA tends to saturate in the low-density range. The DGNs annealed at low temperatures exhibit larger SSA than high-temperature DGNs because of the abundant free edges.

A Nonlinear Rail Vehicle Dynamics Computer Program SAMS/Rail: Part 1—Theory and Formulations

2009 ◽  
Author(s):  
Khaled E. Zaazaa ◽  
Brian Whitten ◽  
Brian Marquis ◽  
Erik Curtis ◽  
Magdy El-Sibaie ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Contact Element ◽  
Contact Forces ◽  
Simulation Code ◽  
Vehicle Performance ◽  
Normal Contact ◽  
Advantages And Disadvantages ◽  
High Speed Trains

Accurate prediction of railroad vehicle performance requires detailed formulations of wheel-rail contact models. In the past, most dynamic simulation tools used an offline wheel-rail contact element based on look-up tables that are used by the main simulation solver. Nowadays, the use of an online nonlinear three-dimensional wheel-rail contact element is necessary in order to accurately predict the dynamic performance of high speed trains. Recently, the Federal Railroad Administration, Office of Research and Development has sponsored a project to develop a general multibody simulation code that uses an online nonlinear three-dimensional wheel-rail contact element to predict the contact forces between wheel and rail. In this paper, several nonlinear wheel-rail contact formulations are presented, each using the online three-dimensional approach. The methods presented are divided into two contact approaches. In the first Constraint Approach, the wheel is assumed to remain in contact with the rail. In this approach, the normal contact forces are determined by using the technique of Lagrange multipliers. In the second Elastic Approach, wheel/rail separation and penetration are allowed, and the normal contact forces are determined by using Hertz’s Theory. The advantages and disadvantages of each method are presented in this paper. In addition, this paper discusses future developments and improvements for the multibody system code. Some of these improvements are currently being implemented by the University of Illinois at Chicago (UIC). In the accompanying “Part 2” and “Part 3” to this paper, numerical examples are presented in order to demonstrate the results obtained from this research.

Thermal Design of Highly-Efficient Thermoelectric Materials With Atomic-Scale Three-Dimensional Phononic Crystals

2007 ◽  
Author(s):  
Jean-Numa Gillet ◽  
Yann Chalopin ◽  
Sebastian Volz
Keyword(s):  
Thermal Conductivity ◽  
Bulk Material ◽  
Phononic Crystal ◽  
Three Dimensional ◽  
Mean Free Path ◽  
Dispersion Curves ◽  
Phononic Crystals ◽  
Thermal Design ◽  
Atomic Scale ◽  
Thermal Insulating

Owing to their thermal insulating properties, superlattices have been extensively studied. A breakthrough in the performance of thermoelectric devices was achieved by using superlattice materials. The problem of those nanostructured materials is that they mainly affect heat transfer in only one direction. In this paper, the concept of canceling heat conduction in the three spatial directions by using atomic-scale three-dimensional (3D) phononic crystals is explored. A period of our atomic-scale 3D phononic crystal is made up of a large number of diamond-like cells of silicon atoms, which form a square supercell. At the center of each supercell, we substitute a smaller number of Si diamond-like cells by other diamond-like cells, which are composed of germanium atoms. This elementary heterostructure is periodically repeated to form a Si/Ge 3D nanostructure. To obtain different atomic configurations of the phononic crystal, the number of Ge diamond-like cells at the center of each supercell can be varied by substitution of Si diamond-like cells. The dispersion curves of those atomic configurations can be computed by lattice dynamics. With a general equation, the thermal conductivity of our atomic-scale 3D phononic crystal can be derived from the dispersion curves. The thermal conductivity can be reduced by at least one order of magnitude in an atomic-scale 3D phononic crystal compared to a bulk material. This reduction is due to the decrease of the phonon group velocities without taking into account that of the phonon average mean free path.

A Greenwood-Williamson Model of Small-Scale Friction

2005 ◽  
Vol 74 (1) ◽  
pp. 31-40 ◽  
Author(s):  
Reese E. Jones
Keyword(s):  
Numerical Method ◽  
Recursion Formula ◽  
Three Dimensional ◽  
Interfacial Friction ◽  
Small Scale ◽  
Analytical Estimate ◽  
Normal Loading ◽  
Proposed Model ◽  
Loading Case ◽  
Transition Length

A Greenwood and Williamson based model for interfacial friction is presented that incorporates the presliding transition phenomenon that can significantly affect small devices. This work builds on previous similar models by developing: an analytical estimate of the transition length in terms of material and surface parameters, a general recursion formula for the case of slip in one direction with multiple reversals and constant normal loading, and a numerical method for the general three-dimensional loading case. In addition, the proposed model is developed within a plasticity-like framework and is shown to have qualitative similarities with published experimental observations. A number of model problems illustrate the response of the proposed model to various loading conditions.

An Extension of CEB Elastic-Plastic Contact Model

2007 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Contact Force ◽  
Tangential Force ◽  
Three Dimensional ◽  
Tangential Direction ◽  
Asperity Contact ◽  
Force Component ◽  
Normal Contact ◽  
Elastic Plastic ◽  
Force Components ◽  
Plastic Parts

Three dimensional elastic-plastic contact of two nominally flat rough surfaces is by developing the equations governing the shoulder-shoulder contact of asperities based on the Chang, Etsion and Bogy (CEB) model of contact in which volume conservation is assumed in the plastic flow regime. Shoulder-shoulder asperity contact yields a slanted contact force consisting of both tangential (parallel to mean plane) and normal components. Each force component comprises elastic and elastic-plastic parts. Statistical summation of normal force components leads to the derivation of the normal contact force for the elastic-plastic contact akin to the CEB model. Half-plane tangential force due to elastic-plastic contact is derived through the statistical summation of tangential force component along an arbitrary tangential direction.

scholarly journals Nanometer Scale Tomographic Investigation of Fine Scale Precipitates in a CuFeNi Granular System by Three-Dimensional Field Ion Microscopy

2012 ◽  
Vol 18 (5) ◽  
pp. 1129-1134 ◽  
Author(s):  
Sophie Cazottes ◽  
François Vurpillot ◽  
Abdeslem Fnidiki ◽  
Dany Lemarchand ◽  
Marcello Baricco ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Precise Determination ◽  
Atomic Scale ◽  
Granular System ◽  
Field Ion Microscopy ◽  
Mean Diameter ◽  
The Matrix ◽  
The Mean ◽  
Ion Microscopy

AbstractThe microstructure of Cu80Fe10Ni10 (at. %) granular ribbons was investigated by means of three-dimensional field ion microscopy (3D FIM). This ribbon is composed of magnetic precipitates embedded in a nonmagnetic matrix. The magnetic precipitates have a diameter smaller than 5 nm in the as-spun state and are coherent with the matrix. No accurate characterization of such a microstructure has been performed so far. A tomographic characterization of the microstructure of melt spun and annealed Cu80Fe10Ni10 ribbon was achieved with 3D FIM at the atomic scale. A precise determination of the size distribution, number density, and distance between the precipitates was carried out. The mean diameter for the precipitates is 4 nm in the as-spun state. After 2 h at 350°C, there is an increase of the size of the precipitates, while after 2 h at 400°C the mean diameter of the precipitates decreases. Those data were used as inputs in models that describe the magnetic and magnetoresistive properties of this alloy.

Three-dimensional atomic-scale investigation of ZnO-MgxZn1−xO m-plane heterostructures

2017 ◽  
Vol 111 (3) ◽  
pp. 032108 ◽  
Author(s):  
E. Di Russo ◽  
L. Mancini ◽  
F. Moyon ◽  
S. Moldovan ◽  
J. Houard ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Atomic Scale
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