167 research outputs found
Imaging the stick-slip peeling of an adhesive tape under a constant load
Using a high speed camera, we study the peeling dynamics of an adhesive tape
under a constant load with a special focus on the so-called stick-slip regime
of the peeling. It is the first time that the very fast motion of the peeling
point is imaged. The speed of the camera, up to 16000 fps, allows us to observe
and quantify the details of the peeling point motion during the stick and slip
phases: stick and slip velocities, durations and amplitudes. First, in contrast
with previous observations, the stick-slip regime appears to be only transient
in the force controlled peeling. Additionally, we discover that the stick and
slip phases have similar durations and that at high mean peeling velocity, the
slip phase actually lasts longer than the stick phase. Depending on the mean
peeling velocity, we also observe that the velocity change between stick and
slip phase ranges from a rather sudden to a smooth transition. These new
observations can help to discriminate between the various assumptions used in
theoretical models for describing the complex peeling of an adhesive tape. The
present imaging technique opens the door for an extensive study of the velocity
controlled stick-slip peeling of an adhesive tape that will allow to understand
the statistical complexity of the stick-slip in a stationary case
On slip pulses at a sheared frictional viscoelastic/ non deformable interface
We study the possibility for a semi-infinite block of linear viscoelastic
material, in homogeneous frictional contact with a non-deformable one, to slide
under shear via a periodic set of ``self-healing pulses'', i.e. a set of
drifting slip regions separated by stick ones. We show that, contrary to
existing experimental indications, such a mode of frictional sliding is
impossible for an interface obeying a simple local Coulomb law of solid
friction. We then discuss possible physical improvements of the friction model
which might open the possibility of such dynamics, among which slip weakening
of the friction coefficient, and stress the interest of developing systematic
experimental investigations of this question.Comment: 23 pages, 3 figures. submitted to PR
Contact mechanics for randomly rough surfaces
When two solids are squeezed together they will in general not make atomic
contact everywhere within the nominal (or apparent) contact area. This fact has
huge practical implications and must be considered in many technological
applications. In this paper I briefly review basic theories of contact
mechanics. I consider in detail a recently developed contact mechanics theory.
I derive boundary conditions for the stress probability distribution function
for elastic, elastoplastic and adhesive contact between solids and present
numerical results illustrating some aspects of the theory. I analyze contact
problems for very smooth polymer (PMMA) and Pyrex glass surfaces prepared by
cooling liquids of glassy materials from above the glass transition
temperature. I show that the surface roughness which results from the frozen
capillary waves can have a large influence on the contact between the solids.
The analysis suggest a new explanation for puzzling experimental results [L.
Bureau, T. Baumberger and C. Caroli, arXiv:cond-mat/0510232] about the
dependence of the frictional shear stress on the load for contact between a
glassy polymer lens and flat substrates. I discuss the possibility of testing
the theory using numerical methods, e.g., finite element calculations.Comment: Review paper, 29 pages, 31 picture
Comparison between the adherence of a rigid axisymmetrical cone and a truncated one, in adhesive contact on an elastic half-space
Adhesive contact of a conical punch on an elastic half-space
It is shown that the Sneddon general theory (1965) enables the contact of axisymmetric adhesive punches to be studied. The relation between load and penetration, and the adherence force for conical punch are given.On montre que la théorie générale de Sneddon (1965) permet d'étudier les contacts de poinçons axisymétriques adhésifs. On donne la relation entre charge et pénétration, et la force d'adhérence pour un cône de révolution
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