100 research outputs found
On the dependence of the leak-rate of seals on the skewness of the surface height probability distribution
Seals are extremely useful devices to prevent fluid leakage. We present
experimental result which show that the leak-rate of seals depend sensitively
on the skewness in the height probability distribution. The experimental data
are analyzed using the critical-junction theory. We show that using the
top-power spectrum result in good agreement between theory and experiment.Comment: 5 pages, 9 figure
Leak-rate of seals: effective medium theory and comparison with experiment
Seals are extremely useful devices to prevent fluid leakage. We present an
effective medium theory of the leak-rate of rubber seals, which is based on a
recently developed contact mechanics theory. We compare the theory with
experimental results for seals consisting of silicon rubber in contact with
sandpaper and sand-blasted PMMA surfaces.Comment: 8 pages, 11 figure
Leak-rate of seals: comparison of theory with experiment
Seals are extremely useful devices to prevent fluid leakage. We present
experimental results for the leak-rate of rubber seals, and compare the results
to a novel theory, which is based on percolation theory and a recently
developed contact mechanics theory. We find good agreement between theory and
experiment.Comment: 6 pages, 10 figure
Fluid flow at the interface between elastic solids with randomly rough surfaces
I study fluid flow at the interface between elastic solids with randomly
rough surfaces. I use the contact mechanics model of Persson to take into
account the elastic interaction between the solid walls and the Bruggeman
effective medium theory to account for the influence of the disorder on the
fluid flow. I calculate the flow tensor which determines the pressure flow
factor and, e.g., the leak-rate of static seals. I show how the perturbation
treatment of Tripp can be extended to arbitrary order in the ratio between the
root-mean-square roughness amplitude and the average interfacial surface
separation. I introduce a matrix D(Zeta), determined by the surface roughness
power spectrum, which can be used to describe the anisotropy of the surface at
any magnification Zeta. I present results for the asymmetry factor Gamma(Zeta)
(generalized Peklenik number) for grinded steel and sandblasted PMMA surfaces.Comment: 16 pages, 14 figure
Heat transfer between elastic solids with randomly rough surfaces
We study the heat transfer between elastic solids with randomly rough
surfaces. We include both the heat transfer from the area of real contact, and
the heat transfer between the surfaces in the noncontact regions. We apply a
recently developed contact mechanics theory, which accounts for the
hierarchical nature of the contact between solids with roughness on many
different length scales. For elastic contact, at the highest (atomic)
resolution the area of real contact typically consists of atomic (nanometer)
sized regions, and we discuss the implications of this for the heat transfer.
For solids with very smooth surfaces, as is typical in many modern engineering
applications, the interfacial separation in the non-contact regions will be
very small, and for this case we show the importance of the radiative heat
transfer associated with the evanescent electromagnetic waves which exist
outside of all bodies.Comment: 23 pages, 19 figure
Fluid squeeze-out between rough surfaces: comparison of theory with experiment
We study the time dependency of the (average) interfacial separation between
an elastic solid with a flat surface and a rigid solid with a randomly rough
surface, squeezed together in a fluid. We use an analytical theory describing
the fluid flow factors, based on the Persson contact mechanics theory and the
Bruggeman effective medium theory, to calculate the removal of the fluid from
the contacting interface of the two solids. In order to test this approach, we
have performed simple squeeze-out experiments. The experimental results are
compared to the theory predictions.Comment: 8 pages, 13 figure
Contact mechanics with adhesion: Interfacial separation and contact area
We study the adhesive contact between elastic solids with randomly rough,
self affine fractal surfaces. We present molecular dynamics (MD) simulation
results for the interfacial stress distribution and the wall-wall separation.
We compare the MD results for the relative contact area and the average
interfacial separation, with the prediction of the contact mechanics theory of
Persson. We find good agreement between theory and the simulation results. We
apply the theory to the system studied by Benz et al. involving polymer in
contact with polymer, but in this case the adhesion gives only a small
modification of the interfacial separation as a function of the squeezing
pressure.Comment: 5 pages, 4 figure
Interfacial separation between elastic solids with randomly rough surfaces: comparison of experiment with theory
We study the average separation between an elastic solid and a hard solid
with a nominal flat but randomly rough surface, as a function of the squeezing
pressure. We present experimental results for a silicon rubber (PDMS) block
with a flat surface squeezed against an asphalt road surface. The theory shows
that an effective repulse pressure act between the surfaces of the form p
proportional to exp(-u/u0), where u is the average separation between the
surfaces and u0 a constant of order the root-mean-square roughness, in good
agreement with the experimental results.Comment: 6 pages, 10 figure
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