On Pastewka and Robbins' Criterion for Macroscopic Adhesion of Rough Surfaces

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
M. Ciavarella
Keyword(s):  
Rough Surface ◽  
Root Mean Square ◽  
Rough Surfaces ◽  
Mean Square ◽  
Asperity Model ◽  
Factor Α ◽  
Rms Amplitude ◽  
Simplified Form

Pastewka and Robbins (2014, “Contact Between Rough Surfaces and a Criterion for Macroscopic Adhesion,” Proc. Natl. Acad. Sci., 111(9), pp. 3298–3303) recently have proposed a criterion to distinguish when two surfaces will stick together or not and suggested that it shows quantitative and qualitative large conflicts with asperity theories. However, a comparison with asperity theories is not really attempted, except in pull-off data which show finite pull-off values in cases where both their own criterion and an asperity based one seem to suggest nonstickiness, and the results are in these respects inconclusive. Here, we find that their criterion corresponds very closely to an asperity model one (provided we use their very simplified form of the Derjaguin–Muller–Toporov (DMT) adhesion regime which introduces a dependence on the range of attractive forces) when bandwidth α is small, but otherwise involves a root-mean-square (RMS) amplitude of roughness reduced by a factor α. Therefore, it implies that the stickiness of any rough surface is the same as that of the surface where practically all the wavelength components of roughness are removed except the very fine ones.

A New Adaptive-Surface Elastic-Plastic Contact Model of Rough Surfaces: Parameter Correlations

2006 ◽  
Vol 532-533 ◽  
pp. 961-964
Author(s):  
Min Song
Keyword(s):  
Rough Surface ◽  
Root Mean Square ◽  
Rough Surfaces ◽  
Computing Time ◽  
Contact Model ◽  
Asperity Contact ◽  
Mean Square ◽  
Elastic Plastic ◽  
Surface Profiles

Based on an presented adaptive-surface elastic-plastic asperity contact model which can greatly decrease contact computing time and keep the precision loss less than 5%, a series of 2-D rough surface profiles with different roughness and correlative length are numerically generated to investigate how to select the threshold used in this model for different adaptive rough surfaces. The results show that well acceptable precision of the elastic-plastic contact calculation would be derived when the ratio of threshold to root mean square curvature, δ 1.0 10 6mm2 − < × .

Direct numerical simulation of turbulence over systematically varied irregular rough surfaces

2019 ◽  
Vol 862 ◽  
pp. 781-815 ◽  
Author(s):  
Y. Kuwata ◽  
Y. Kawaguchi
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Root Mean Square ◽  
Drag Force ◽  
Rough Surfaces ◽  
Skin Friction Coefficient ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Mean Velocity ◽  
Navier Stokes Equation

Lattice Boltzmann direct numerical simulation of turbulent open-channel flows over randomly distributed hemispheres at $Re_{\unicode[STIX]{x1D70F}}=600$ is carried out to reveal the influence of roughness parameters related to a probability density function of rough-surface elevation on turbulence by analysing the spatial and Reynolds- (double-) averaged Navier–Stokes equation. This study specifically concentrates on the influence of the root-mean-square roughness and the skewness, and profiles of turbulence statistics are compared by introducing an effective wall-normal distance defined as a wall-normal integrated plane porosity. The effective distance can completely collapse the total shear stress outside the roughness sublayer, and thus the similarity of the streamwise mean velocity is clearer by introducing the effective distance. In order to examine the influence of the root-mean-square roughness and the skewness on dynamical effects that contribute to an increase in the skin friction coefficient, the triple-integrated double-averaged Navier–Stokes equation is analysed. The main contributors to the skin friction coefficient are found to be turbulence and drag force. The turbulence contribution increases with the root-mean-square roughness and/or the skewness. The drag force contribution, on the other hand, increases in particular with the root-mean-square roughness whereas an increase in the skewness does not increase the drag force contribution because it does not necessarily increase the surface area of the roughness elements. The contribution of the mean velocity dispersion induced by spatial inhomogeneity of the rough surfaces substantially increases with the root-mean-square roughness. A linear correlation is confirmed between the root-mean-square roughness and the equivalent roughness while the equivalent roughness monotonically increases with the skewness. A new correlation function based on the root-mean-square roughness and the skewness is developed with the available experimental and direct numerical simulation data, and it is confirmed that the developed correlation reasonably predicts the equivalent roughness of various types of real rough surfaces.

On the Nature of O-Rings in Contact With Rough Surfaces

1988 ◽  
Vol 110 (4) ◽  
pp. 632-637 ◽  
Author(s):  
W. E. Warren ◽  
J. G. Curro ◽  
D. E. Amos
Keyword(s):  
Theoretical Analysis ◽  
Root Mean Square ◽  
Contact Pressure ◽  
Contact Force ◽  
Rough Surfaces ◽  
Fundamental Importance ◽  
Elastic Behavior ◽  
Surface Irregularity ◽  
Mean Square ◽  
Irregular Surfaces

This work provides a theoretical analysis of the elastic behavior of an O-ring compressed between two rigid plates with irregular surfaces. Relations between deflection, contact force and contact pressure are obtained. The contact pressure, which is of fundamental importance in establishing criteria for effective sealing, is dependent upon both the amplitude and wavelength of the surface irregularity. This analysis suggests that surfaces in contact with O-ring seals should be characterized by the root mean square slope Δq in addition to the usual Ra which depends on amplitude only.

Simulation on Composite Backscattering from Rough Surface with Target above it

2012 ◽  
Vol 490-495 ◽  
pp. 603-607
Author(s):  
Wei Tian ◽  
Xin Cheng Ren
Keyword(s):  
Rough Surface ◽  
Root Mean Square ◽  
Cross Section ◽  
Correlation Length ◽  
Rectangular Cross Section ◽  
Mean Square ◽  
Method Of Moment ◽  
Backscattering Coefficient ◽  
One Dimensional ◽  
Surface Fluctuation

One-dimensional Gaussion rough surface is simulated and employed by Monte Carlo Method, the composite backscattering from one-dimensional Gaussion rough surface with rectangular cross-section column above it is studied using Method of Moment. The curves of composite backscattering coefficient with scattering angle and frequency of incident wave are simulated by numerical calculation, the influence of the root mean square and the correlation length of rough surface fluctuation, the height between the center of the rectangular cross-section column and the rough surface, the length and the width of the rectangular cross-section column is discussed. The characteristic of the composite back-scatting from one-dimensional Gaussion rough surface with a rectangular cross-section column above it is obtained. The results show that the influences of the root mean square and the correlation length of rough surface fluctuation, the height between the center of the rectangular cross-section column and the rough surface, the width of the rectangular cross-section column on the composite backscattering coefficients are obvious while the influences of the length of the rectangular cross-section column on the complex backscattering coefficient is less.

scholarly journals Elastic Rough Surface Contact and the Root Mean Square Slope of Measured Surfaces over Multiple Scales

2021 ◽  
Vol 5 (2) ◽  
pp. 44
Author(s):  
Robert Jackson ◽  
Yang Xu ◽  
Swarna Saha ◽  
Kyle Schulze
Keyword(s):  
Rough Surface ◽  
Root Mean Square ◽  
Contact Area ◽  
Multiple Scales ◽  
Real Contact Area ◽  
Mean Square ◽  
The Real ◽  
Real Contact ◽  
Surface Contact ◽  
Rough Surface Contact

This study investigates the predictions of the real contact area for perfectly elastic rough surfaces using a boundary element method (BEM). Sample surface measurements were used in the BEM to predict the real contact area as a function of load. The surfaces were normalized by the root-mean-square (RMS) slope to evaluate if contact area measurements would collapse onto one master curve. If so, this would confirm that the contact areas of manufactured, real measured surfaces are directly proportional to the root mean square slope and the applied load, which is predicted by fractal diffusion-based rough surface contact theory. The data predicts a complex response that deviates from this behavior. The variation in the RMS slope and the spectrum of the system related to the features in contact are further evaluated to illuminate why this property is seen in some types of surfaces and not others.

scholarly journals Deterministic normal contact of rough surfaces with adhesion using a surface integral method

2020 ◽  
Vol 476 (2242) ◽  
pp. 20200281 ◽  
Author(s):  
Ali Ghanbarzadeh ◽  
Mostafa Faraji ◽  
Anne Neville
Keyword(s):  
Surface Roughness ◽  
Root Mean Square ◽  
Fundamental Problem ◽  
Rough Surfaces ◽  
Adhesive Contact ◽  
Mean Square ◽  
Surface Integral ◽  
Normal Contact ◽  
Surface Integration ◽  
Effect Of Surface

The fundamental problem of adhesion in the presence of surface roughness and its effect on the prediction of friction has been a hot topic for decades in numerous areas of science and engineering, attracting even more attention in recent years in areas such as geotechnics and tectonics, nanotechnology, high-value manufacturing and biomechanics. In this paper a new model for deterministic calculation of the contact mechanics for rough surfaces in the presence of adhesion is presented. The contact solver is an in-house boundary element method that incorporates fast Fourier transform for numerical efficiency. The adhesive contact model considers full Lennard-Jones potentials and surface integration at the asperity level and is validated against models in the literature. Finally, the effect of surface roughness on the adhesion between surfaces was studied, and it was shown that the root mean square gradient of surface roughness can change the adhesive pressures irrespective of the root mean square surface roughness. We have tested two adhesion parameters based on Johnson's modified criteria and Ciavarella's model. We showed that Civarella's model introduces the most reasonable criteria suggesting that the RMS roughness and large wavelength of surfaces roughness are the important parameters of adhesion between rough surfaces.

About rms amplitude of zero oscillations of atoms in crystal

2021 ◽  
pp. 48-53
Author(s):  
I. Khidirov ◽  
◽  
S.Dj. Rakhmanov ◽  
Sh.A. Makhmudov ◽  
◽  
...  
Keyword(s):  
Debye Temperature ◽  
Root Mean Square ◽  
Room Temperature ◽  
Materials Science ◽  
Ordinal Number ◽  
Zero Point ◽  
Mean Square ◽  
Root Mean Square Amplitude ◽  
Thermal Vibrations ◽  
Rms Amplitude

It is shown that the values of the energy and amplitude of zero-point vibrations of atoms in a crystal, due to the uncertainty principle, depend on the dynamic characteristics of atoms in the crystal. It was found that the root-mean-square amplitude of thermal and zero-point vibrations of atoms, like other properties, has a periodic dependence on the ordinal number of elements in the Mendeleev's Periodic Table. It is shown that the value of the root-mean-square amplitude of thermal vibrations of atoms in a lattice of elements with a high value of the Debye temperature at room temperature does not differ much from the value of the amplitude of zero-point vibrations of atoms (at T = 0 K). This is explained by the small number of excited vibrations with the maximum frequency in these crystals at room temperature, since the room temperature is much lower than their Debye temperature, at which the entire spectrum of thermal vibrations of atoms in the crystal is excited. The results can be used in materials science and technology to assess the strength and thermo physical characteristics of materials at cryogenic temperatures, without resorting to measuring them directly at absolute zero.

Roughness Perception of Haptically Displayed Fractal Surfaces

2000 ◽  
Author(s):  
Michael A. Costa ◽  
Mark R. Cutkosky
Keyword(s):  
Fractal Dimension ◽  
Root Mean Square ◽  
Force Feedback ◽  
Mean Square ◽  
Fractal Surfaces ◽  
Surface Profiles ◽  
Rms Amplitude ◽  
Roughness Perception

Abstract Surface profiles were generated by a fractal algorithm and haptically rendered on a force feedback joystick. Subjects were asked to use the joystick to explore pairs of surfaces and report to the experimenter which of the surfaces they felt was rougher. Surfaces were characterized by their root mean square (RMS) amplitude and their fractal dimension. The most important factor affecting the perceived roughness of the fractal surfaces was the RMS amplitude of the surface. When comparing surfaces of fractal dimension 1.2–1.35 it was found that the fractal dimension was negatively correlated with perceived roughness.

A mechanical-reflex oscillator hypothesis for parkinsonian hand tremor

1976 ◽  
Vol 40 (6) ◽  
pp. 990-998 ◽  
Author(s):  
R. N. Stiles ◽  
R. S. Pozos
Keyword(s):  
Spectral Analysis ◽  
Steady State ◽  
Root Mean Square ◽  
Fold Increase ◽  
Normal Subjects ◽  
Single Frequency ◽  
Mean Square ◽  
Hand Tremor ◽  
S Period ◽  
Rms Amplitude

Spectral analysis was performed on postural hand tremor records obtained from 22 parkinsonian subjects. Of these 22 subjects, 18 had postural hand tremor that occurred primarily at a single frequency during any one 16-s period. In general, this tremor occurred at different steady-state frequencies (each calculated over 16 s) between about 4 Hz and 8–9 Hz. This frequency decreased approximately 1 Hz for each 10-fold increase in displacement amplitude (root-mean-square, rms, amplitude determined at 16 cm from the wrist), decreasing from 8–9 Hz at about 30 mum to 3.75–4.0 Hz at about 30,000 mum. The major finding was that the frequency of parkinsonian hand tremor was nearly the same as that for hand tremor from normal subjects when these frequenceis were compared at similar rms displacement levels. This comparison, plus a comparison between other aspects of these two kinds of tremor, indicate that the mechanism for parkinsonian hand tremor is similar to that for large-displacement (greater than 100 mum) hand tremor of normal subjects, i.e., a mechanical-reflex oscillator mechanism.

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