Effects of Friction on Contact of Transverse Ground Surfaces

1994 ◽  
Vol 116 (3) ◽  
pp. 430-437 ◽  
Author(s):  
J. B. Mann ◽  
T. N. Farris ◽  
S. Chandrasekar
Keyword(s):  
Rough Surface ◽  
Contact Pressure ◽  
Smooth Surface ◽  
Bulk Material ◽  
Elastic Half Space ◽  
Material Surface ◽  
Asperity Contact ◽  
Hertz Contact ◽  
Effective Stresses ◽  
Subsurface Stress

The two-dimensional plane-strain sliding contact of a smooth rigid roller on a transverse ground rough surface is analyzed. The rough surface is idealized as an elastic half-space with periodic roughness modeled as cylindrical ridges oriented transverse to the sliding direction. The contact problem is solved using a numerical iterative method in which each asperity contact is treated as a micro-Hertz contact, and the exact treatment of asperity interaction is included. The subsurface stress field is calculated using Westergaard stress functions. The subsequent analysis compares the rough surface stress fields with the corresponding smooth Hertz contact to evaluate the influence of surface roughness and friction on the subsurface stress distributions. The results show that the real area of contact is less than the corresponding smooth surface Hertz contact area, and the magnitude of the actual localized maximum contact pressure is always greater than the corresponding smooth surface contact pressure. The asperity level subsurface effective stresses are greater in magnitude than the maximum subsurface stress due to the macro-Hertz contact for low coefficients of friction, and for high coefficients of friction the maximum effective stresses occur on the bulk material surface.

scholarly journals Linear and Nonlinear Normal Interface Stiffness in Dry Rough Surface Contact Measured Using Longitudinal Ultrasonic Waves

2021 ◽  
Vol 11 (12) ◽  
pp. 5720
Author(s):  
Saeid Taghizadeh ◽  
Robert Sean Dwyer-Joyce
Keyword(s):  
Rough Surface ◽  
Contact Pressure ◽  
Ultrasonic Wave ◽  
Bulk Material ◽  
Nonlinear Differential Equations ◽  
Small Deformation ◽  
Ultrasonic Waves ◽  
Solid Contact ◽  
Interfacial Stiffness ◽  
Linear And Nonlinear

When two rough surfaces are loaded together contact occurs at asperity peaks. An interface of solid contact regions and air gaps is formed that is less stiff than the bulk material. The stiffness of a structure thus depends on the interface conditions; this is particularly critical when high stiffness is required, for example in precision systems such as machine tool spindles. The rough surface interface can be modelled as a distributed spring. For small deformation, the spring can be assumed to be linear; whilst for large deformations the spring gets stiffer as the amount of solid contact increases. One method to measure the spring stiffness, both the linear and nonlinear aspect, is by the reflection of ultrasound. An ultrasonic wave causes a perturbation of the contact and the reflection depends on the stiffness of the interface. In most conventional applications, the ultrasonic wave is low power, deformation is small and entirely elastic, and the linear stiffness is measured. However, if a high-powered ultrasonic wave is used, this changes the geometry of the contact and induces nonlinear response. In previous studies through transmission methods were used to measure the nonlinear interfacial stiffness. This approach is inconvenient for the study of machine elements where only one side of the interface is accessible. In this study a reflection method is undertaken, and the results are compared to existing experimental work with through transmission. The variation of both linear and nonlinear interfacial stiffnesses was measured as the nominal contact pressure was increased. In both cases interfacial stiffness was expressed as nonlinear differential equations and solved to deduce the contact pressure-relative surface approach relationships. The relationships derived from linear and nonlinear measurements were similar, indicating the validity of the presented methods.

scholarly journals Cylinder-Flat Contact Mechanics with Surface Roughness

2020 ◽  
Vol 69 (1) ◽  
Author(s):  
A. Tiwari ◽  
B. N. J. Persson
Keyword(s):  
Surface Roughness ◽  
Contact Pressure ◽  
Dimensionless Parameter ◽  
Elastic Half Space ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Hertz Contact ◽  
Random Surface ◽  
Roughness Amplitude ◽  
Flat Contact

AbstractWe study the nominal (ensemble averaged) contact pressure p(x) acting on a cylinder squeezed in contact with an elastic half space with random surface roughness. The contact pressure is Hertzian-like for $$\alpha < 0.01$$ α < 0.01 and Gaussian-like for $$\alpha > 10$$ α > 10 , where the dimensionless parameter $$\alpha = h_{\rm rms}/\delta $$ α = h rms / δ is the ratio between the root-mean-square roughness amplitude and the penetration for the smooth surfaces case (Hertz contact).

A Rough Surface Contact Model for General Anisotropic Materials

2004 ◽  
Vol 126 (1) ◽  
pp. 41-49 ◽  
Author(s):  
Yuan Lin ◽  
Timothy C. Ovaert
Keyword(s):  
Rough Surface ◽  
Half Space ◽  
Contact Pressure ◽  
Surface Displacement ◽  
Anisotropic Materials ◽  
Elastic Half Space ◽  
Iteration Scheme ◽  
Real Contact Area ◽  
Surface Contact ◽  
Rough Surface Contact

A method for solving the two-dimensional (2-D) isothermal rough surface contact problem of general anisotropic materials with friction is presented. By using Stroh’s formalism, the surface displacements of an elastic half-space due to uniform distributions of traction over a strip are derived from the surface Green’s function. The surface displacement and subsurface stresses of the anisotropic half-space due to the distributed contact pressure may then be calculated by superposition. The real contact area and the contact pressure are determined via an iteration scheme using the conjugate gradient method.

Numerical Contact Model of a Smooth Ball on an Anisotropic Rough Surface

1994 ◽  
Vol 116 (2) ◽  
pp. 194-201 ◽  
Author(s):  
C. Y. Poon ◽  
R. S. Sayles
Keyword(s):  
Rough Surface ◽  
Contact Pressure ◽  
Smooth Surface ◽  
Contact Model ◽  
The Real ◽  
Numerical Result ◽  
Realistic Situation ◽  
Surface Contact ◽  
Rough Surface Contact ◽  
Sinusoidal Surface

A numerical elastic-plastic contact model of a smooth ball on a directionally structured anisotropic rough surface is presented. The contact model is tested on three types of surface contact of a smooth ball on (i) a smooth surface, (ii) a sinusoidal surface, and (iii) a real rough surface. The validity of the model is proven by good agreement of the numerical result for the smooth surface with the Hertz analytical result. The contact of the sinusoidal surface shows that by the introduction of surface undulation in a regular pattern, the real pressure distribution follows the expected behavior where the contact pressure at the peak is maximum and the contact pressure at the valley is zero and the peak pressure decreases away from the ball center. The contact of the real rough surface shows the ability of the model to cope with the more practically realistic situation where the asperity heights are distributed randomly. The results of the rough surface contact analysis for different surface roughness are presented in a separate paper.

An Improved Elastic Contact Model Accounting for Asperity Interaction and Bulk Substrate Deformation

2009 ◽  
Author(s):  
Jungkyu Lee ◽  
Chang-Dong Yeo ◽  
Andreas A. Polycarpou
Keyword(s):  
Rough Surface ◽  
Contact Stiffness ◽  
Elastic Half Space ◽  
Contact Model ◽  
Asperity Contact ◽  
Single Asperity ◽  
Surface Contact ◽  
In Series ◽  
Bulk Substrate ◽  
Rough Surface Contact

An improved rough surface contact model is proposed accounting for bulk substrate deformation and asperity interaction. The asperity contact stiffness is based on Hertzian solution for spherical contact, and the bulk substrate stiffness on the solution of Hertzian pressure on a circular region of the elastic half-space. The contact behavior of a single asperity composed of hemi-spherical asperity deformation as well as bulk substrate deformation is calculated by introducing the concept of spring-in-series. Based on the single asperity model, the contact stiffness for the rough surface is calculated including the effect of asperity interaction. Analytical simulation results using the proposed rough surface contact model were compared with the CEB model and experimental measurements.

Investigations Into Asperity Persistence in Heavily Loaded Contacts

1999 ◽  
Vol 121 (3) ◽  
pp. 441-448 ◽  
Author(s):  
I. Lee-Prudhoe ◽  
R. S. Sayles ◽  
A. Kaderic
Keyword(s):  
Rough Surface ◽  
Simulation Models ◽  
Simulation Method ◽  
Asperity Contact ◽  
Local Contact ◽  
Before And After ◽  
Indentation Tests ◽  
Mechanisms Of Persistence ◽  
Contact Pressures ◽  
Smooth Roller

Experimental results are presented along the lines of the early work of Moore (1948) where a hard smooth roller is pressed into a softer rough surface to study the resulting real to apparent areas of contact and their associated local contact pressures. Results are presented for a hard steel roller deforming mild-steel and aluminum-alloy rough surface specimens. An analysis of the local contact mechanics is performed before and after indentation using a recently developed numerical elastic contact simulation method which allows local asperity contact pressures and areas to be studied in detail. The method is shown to reveal the level and distribution of pressures and asperity contact areas prevalent during the indentation process, and therefore allows the contribution of elastic and plastic load support to be quantified. The persistence of asperities during such indentation tests is discussed in terms of the pressures the asperities can support in relation to reported mechanisms of persistence. Results of subsequent sub-surface stresses are also presented and discussed in terms of how the method might be used to create an elastic-plasticdeformation model that can account for asperity persistence in future numerical contact simulation models.

Design Optimization of Ultra-Low Flying Head-Disk Interfaces Using an Improved Elastic-Plastic Rough Surface Model

2006 ◽  
Vol 128 (4) ◽  
pp. 801-810 ◽  
Author(s):  
Allison Y. Suh ◽  
Sung-Chang Lee ◽  
Andreas A. Polycarpou
Keyword(s):  
Rough Surface ◽  
Contact Pressure ◽  
Surface Model ◽  
Successful Implementation ◽  
Contact Conditions ◽  
Friction Forces ◽  
Interfacial Forces ◽  
Elastic Plastic ◽  
The Mean ◽  
Improved Model

Sub-5nm flying head-disk interfaces (HDIs) designed to attain extremely high areal recording densities of the order of Tbit∕in2 are susceptible to strong adhesive forces, which can lead to subsequent contact, bouncing vibration, and high friction. Accurate prediction of the relevant interfacial forces can help ensure successful implementation of ultra-low flying HDIs. In this study, an improved rough surface model is developed to estimate the adhesive, contact, and friction forces as well as the mean contact pressure relevant to sub-5nm HDIs. The improved model was applied to four different HDIs of varying roughness and contact conditions, and was compared to the sub-boundary lubrication rough surface model. It was found that the interfacial forces in HDIs undergoing primarily elastic-plastic and plastic contact are more accurately predicted with the improved model, while under predominantly elastic contact conditions, the two models give similar results. The improved model was then used to systematically investigate the effect of roughness parameters on the interfacial forces and mean contact pressure (response). The trends in the responses were investigated via a series of regression models using a full 33 factorial design. It was found that the adhesive and net normal interfacial forces increase with increasing mean radius R of asperities when the mean separation is small (≈0.5nm), i.e., pseudo-contacting interface, but it increases primarily with increasing root-mean-square (rms) surface height roughness between 2 and 4nm, i.e., pseudo-flying interface. Also, increasing rms roughness and decreasing R, increases the contact force and mean contact pressure, while the same design decreases the friction force. As the directions of optimization for minimizing the individual interfacial forces are not the same, simultaneous optimization is required for a successful ultra-low flying HDI design.

Contact Analysis of a Smooth Ball on an Anisotropic Rough Surface

1994 ◽  
Vol 116 (4) ◽  
pp. 850-859 ◽  
Author(s):  
C. Y. Poon ◽  
R. S. Sayles
Keyword(s):  
Surface Roughness ◽  
Rough Surface ◽  
Stochastic Approach ◽  
Contact Analysis ◽  
Asperity Contact ◽  
Correlation Lengths ◽  
Real Contact ◽  
Rough Surface Contact ◽  
Contact Pressures ◽  
Contact Spots

The effects of surface roughness and waviness upon the real contact areas, gaps between contact spots, and asperity contact pressures were studied. The distribution of real areas, gaps, and contact pressures are presented for different surface roughness, σ and correlation lengths, β*. The load-area relationship is compared to Bush’s model of strongly anisotropic rough surface contact using a stochastic approach.

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.

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