Three-Dimensional Contact Analysis of Elastic-Plastic Layered Media With Fractal Surface Topographies

2000 ◽  
Vol 123 (3) ◽  
pp. 632-640 ◽  
Author(s):  
K. Komvopoulos ◽  
N. Ye
Keyword(s):  
Contact Area ◽  
Three Dimensional ◽  
Homogeneous Medium ◽  
Real Contact Area ◽  
Rigid Sphere ◽  
Real Surface ◽  
Elastic Plastic ◽  
Real Contact ◽  
Fractal Parameters ◽  
Surface Topographies

Three-dimensional rough surfaces were generated using a modified two-variable Weierstrass-Mandelbrot function with fractal parameters determined from real surface images. The number and size of truncated asperities were assumed to follow power-law relations. A finite element model of a rigid sphere in normal contact with a semi-infinite elastic-plastic homogeneous medium was used to obtain a constitutive relation between the mean contact pressure, real contact area, and corresponding representative strain. The contact model was extended to layered media by modifying the constitutive equation of the homogeneous medium to include the effects of the mechanical properties of the layer and substrate materials and the layer thickness. Finite element simulations of an elastic-plastic layered medium indented by a rigid sphere validated the correctness of the modified contact model. Numerical results for the contact load and real contact area are presented for real surface topographies resembling those of magnetic recording heads and smooth rigid disks. The model yields insight into the evolution of elastic, elastic-plastic, and fully plastic deformation at the contact interface in terms of the maximum local surface interference. The dependence of the contact load and real contact area on the fractal parameters and the carbon overcoat thickness is interpreted in light of simulation results obtained for a tri-pad picoslider in contact with a smooth thin-film hard disk.

Unloading Process in Elastic-Plastic Contact of a Rough Surface With a Flat

2008 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Finite Element ◽  
Rough Surface ◽  
Contact Force ◽  
Contact Area ◽  
Three Dimensional ◽  
Integral Form ◽  
Real Contact Area ◽  
Elastic Plastic ◽  
Real Contact ◽  
Approximate Equations

Three dimensional elastic-plastic contact of a nominally flat rough surface and a flat is considered. The asperity level Finite Element based constitutive equations relating contact force and real contact area to the interference is used. The statistical summation of asperity interaction during unloading phase is derived in integral form. Approximate equations are found that describe in closed form contact load as a function of mean plane separation during unloading. The approximate equations provide accuracy to within 6 percent for the unload phase of the contact force.

Strongly Anisotropic Rough Surfaces

1979 ◽  
Vol 101 (1) ◽  
pp. 15-20 ◽  
Author(s):  
A. W. Bush ◽  
R. D. Gibson ◽  
G. P. Keogh
Keyword(s):  
Random Process ◽  
Rough Surface ◽  
Contact Area ◽  
Process Model ◽  
Rough Surfaces ◽  
Plasticity Index ◽  
Real Contact Area ◽  
Elastic Contact ◽  
Elastic Plastic ◽  
Real Contact

The statistics of a strongly anisotropic rough surface are briefly described. The elastic contact of rough surfaces is treated by approximating the summits of a random process model by parabolic ellipsoids and applying the Hertzian solution for their deformation. Load and real contact area are derived as functions of the separation and for all separations the load is found to be approximately proportional to the contact area. The limits of elastic/plastic contact are discussed in terms of the plasticity index.

A Numerical Calculation of the Contact Area and Pressure of Real Surfaces in Sliding Wear

2000 ◽  
Vol 123 (1) ◽  
pp. 27-35 ◽  
Author(s):  
Zhiqiang Liu ◽  
Anne Neville ◽  
R. L. Reuben
Keyword(s):  
Stress Distribution ◽  
Contact Stress ◽  
Contact Area ◽  
Sliding Wear ◽  
Frictional Coefficient ◽  
Real Contact Area ◽  
Homogeneous Distribution ◽  
Frictional Property ◽  
Real Surface ◽  
Real Contact

A numerical simulation technique based on elastic asperity deformation is presented to analyze real surface contact and pressure distributions in sliding wear. The calculations have been applied to experimentally produced surfaces whose topography has been determined using an atomic force microscope. A variational approach is applied to minimize the stored energy in the contact, which determines contact area without additional iteration. Two-dimensional FIR digital filter techniques are used and an FFT procedure is used to improve the efficiency of the filter implementation. The model is used to obtain the pressure distribution, real contact area, and the distribution of real contact area under sliding conditions either parallel or perpendicular to the grinding lay. The calculated results of real contact stress at different stages of wear are given. The calculated and experimental results suggest that the stress distribution of real contact follows an exponential function. The contact stress distribution index β governs the stress distribution form and reflects the performance of the frictional components in sliding wear. The proportion of plastic contact deformation ψ is also related to β; therefore, reflecting the frictional property in sliding wear. The experimental and calculated results show that the smaller frictional coefficient and more homogeneous distribution of stress occur when the sliding direction is parallel rather than perpendicular to the grinding-lay direction.

Impact of a Rigid Sphere on an Elastic Homogeneous Half-Space

2005 ◽  
Vol 127 (2) ◽  
pp. 325-330 ◽  
Author(s):  
J. Yang ◽  
K. Komvopoulos
Keyword(s):  
Finite Element ◽  
Half Space ◽  
Contact Pressure ◽  
Contact Area ◽  
Real Contact Area ◽  
Rigid Sphere ◽  
Small Surface ◽  
Real Contact ◽  
Homogeneous Half Space ◽  
The Mean

The impact of a rigid sphere moving at constant velocity on elastic homogeneous half-space was analyzed by the finite element method. Frictionless dynamic contact was modeled with special contact elements at the half-space surface. A dimensionless parameter, β, was introduced to study the effect of wave propagation on the deformation behavior. For small surface interference (β⩽1), the front of the faster propagating dilatational waves extends up to the contact edge, the real contact area is equal to the truncated area, and the contact pressure distribution is uniform. However, for large surface interference (β>1), the dilatation wave front extends beyond the contact edge, the real contact area is less than the truncated area, and the contact pressure exhibits a Hertzian-like distribution. The mean contact pressure increases abruptly at the instant of initial contact, remains constant for β⩽1, and increases gradually for β>1. Based on finite element results for the subsurface stress, strain, and velocity fields, a simple theoretical model that yields approximate closed-form relationships for the mean contact pressure and kinetic and strain energies of the half-space was derived for small surface interference (β⩽1), and its validity was confirmed by favorable comparisons with finite element results.

On the Mechanism of Contact Between Metal Surfaces: Part 2—The Real Area and the Number of the Contact Points

1968 ◽  
Vol 90 (1) ◽  
pp. 81-88 ◽  
Author(s):  
T. Tsukizoe ◽  
T. Hisakado
Keyword(s):  
Contact Area ◽  
Three Dimensional ◽  
Real Contact Area ◽  
Load Range ◽  
The Real ◽  
Real Contact ◽  
Contact Points ◽  
Theoretical Analyses ◽  
Total Contact Area ◽  
Real Area

Assuming that the distribution curve obtained from the profile curve of the surface has a normal distribution, the relation between the real contact area and the separation is obtained theoretically in the case of ideal plastic flow of the microcontacts. If the asperities are cones of the same angle which depends on the surface roughness, the three-dimensional number and the distribution of the radii of contact points are also deduced theoretically. The results of the theoretical analyses are compared with the experimental results for the real contact areas and the numbers of the contact points. Results show that over the wide load range the average radii of contact points are almost constant; consequently, the total contact area is increased mainly owing to the increase in the number of the contact points.

scholarly journals A New Approach to Explore the Surface Profile of Clay Soil Using White Light Interferometry

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3009 ◽  
Author(s):  
Suchun Yang ◽  
Junwei Liu ◽  
Longfei Xu ◽  
Mingyi Zhang ◽  
Dong-Sheng Jeng
Keyword(s):  
Particle Size ◽  
Compressive Stress ◽  
Contact Area ◽  
White Light ◽  
Clay Soil ◽  
Surface Profile ◽  
Real Contact Area ◽  
Real Surface ◽  
The Real ◽  
Real Contact

In order to have a better understanding of the real contact area of granular materials, the white light interference method is applied to explore the real surface morphology of clay soils under high stress. Analysis of the surface profile indicates that there exists a support point height z0 with the highest distribution frequency. A concept of a real contact region (from z0 to z0 + d90; d90 represents the particle size corresponding to 90% of the volume fraction) is proposed by combining a surface profile with the particle size distribution of clay soil. It was found that under the compressive stress of 106 MPa–529 MPa, the actual contact area ratio of clay soil varies between 0.375 and 0.431. This demonstrates an increasing trend with the rise of stress. On the contrary, the apparent porosity decreases with an increasing stress, varying between 0.554 and 0.525. In addition, as the compressive stress increases, the cumulative frequency of apparent profile height (from z0 − d90 to z0 + d90) has a concentrated tendency with a limited value of 0.9.

An FFT Deterministic Simulation of Elastic Rough Surfaces in Three-Dimensional Contact and Model Analysis

2009 ◽  
Author(s):  
Robert L. Jackson ◽  
Itzhak Green
Keyword(s):  
Contact Area ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Three Dimensional ◽  
Real Contact Area ◽  
Real Contact ◽  
Contact Models ◽  
Surface Profiles ◽  
Rough Surface Contact ◽  
Mathematical Foundations

For practicing engineers in industry it is important to have closed-form, easy to use equations that can be used to predict the real contact area, and relate it to friction, wear, adhesion, and electrical and thermal contact resistance. There are quite a few such models in the literature, but their agreement or their effectiveness has not been determined. This work will use several measured surface profiles to make predictions of contact area and contact force from many elastic contact models and compare them to a deterministic FFT based rough surface contact model. The results show that several of the models show good quantitative and qualitative agreement despite having very different mathematical foundations.

Effect of normal load on the frictional and wear behaviour of carbon fiber in tow-on-tool contact during three-dimensional weaving process

2020 ◽  
pp. 152808372094461
Author(s):  
Ning Wu ◽  
Ximing Xie ◽  
Jie Yang ◽  
Yajie Feng ◽  
Yanan Jiao ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Contact Area ◽  
Normal Load ◽  
Three Dimensional ◽  
Hertzian Contact ◽  
Wear Behaviour ◽  
Real Contact Area ◽  
The Real ◽  
Real Contact ◽  
Fracture Damage

The effect of normal load on the frictional and wear behaviour of carbon fiber is investigated by simulating the tow-on-tool friction relevant to the beating-up motion of three-dimensional (3 D) weaving process. The true number of contact filaments over a range of normal loads is calculated by characterizing the cross-section parameters of carbon tow. The real contact area is calculated on the basis of the filaments amount by Hertzian contact model. The friction force values obtained from multiplying the real contact area with shear strength are closely with the measured results. The coefficient of friction increases with the increase of normal loads. When the normal load is 250, 400 and 600 mN, the tensile loss rate of the carbon tow after friction test is 6.3%, 23.2% and 42.4% respectively. The filaments reveal multiple fracture damage patterns which are caused by stretching, shearing and compression during the weaving process.

Impact of a Rigid Sphere on an Elastic Homogeneous Half-Space

2004 ◽  
Author(s):  
J. Yang ◽  
K. Komvopoulos
Keyword(s):  
Finite Element ◽  
Half Space ◽  
Contact Pressure ◽  
Contact Area ◽  
Real Contact Area ◽  
Rigid Sphere ◽  
Small Surface ◽  
Real Contact ◽  
Homogeneous Half Space ◽  
The Mean

Impact of a rigid sphere moving at constant velocity on elastic homogeneous half-space was analyzed by the finite element method. Frictionless dynamic contact was modeled with special contact elements at the half-space surface. A dimensionless parameter, β, was introduced to study the effect of wave propagation on the deformation behavior. For small surface interference (β), the front of the faster propagating dilatational waves extends up to the contact edge, the real contact area is equal to the truncated area, and the contact pressure distribution is uniform. However, for large surface interference (β ≤ 1), the dilatation wave front extends beyond the contact edge, the real contact area is less than the truncated area, and the contact pressure exhibits a Hertzian-like distribution. The mean contact pressure increases abruptly at the instant of initial contact, remains constant for β ≤ 1, and increases gradually for β > 1. Based on finite element results for the subsurface stress, strain, and velocity fields, and simple theoretical model that yields approximated closed-form relationships for the mean contact pressure and kinetic and strain energies of the half-space was derived for small surface interference (β ≤ 1), and its validity was confirmed by favor comparisons with finite element results.

Sign in / Sign up

Export Citation Format

Share Document