DOI: 10.1140/epje/i2003-10009-7
Self-healing slip pulses and the friction of gelatin gels
T. Baumberger, C. Caroli and O. RonsinGroupe de Physique des Solides (Associé au Centre National de la Recherche Scientifique et aux Universités Paris 6 et 7.) , 2 place Jussieu, 75251 Paris, Cedex 05, France ronsin@gps.jussieu.fr
(Received 7 March 2003 / Published online: 11 June 2003)
Abstract
We present an extensive experimental study and scaling
analysis of friction of gelatin gels on glass. At low driving
velocities, sliding occurs via propagation of periodic self-healing
slip pulses whose velocity is limited by collective diffusion of the
gel network. Healing can be attributed to a frictional instability
occurring at the slip velocity
. For
, sliding is
homogeneous and friction is ruled by the shear-thinning rheology of an
interfacial layer of thickness of order the (nanometric) mesh size,
containing a solution of polymer chain ends hanging from the
network. In spite of its high degree of confinement, the rheology of
this system does not differ qualitatively from known bulk ones. The
observed ageing of the static friction threshold reveals the slow
increase of adhesive bonding between chain ends and glass. Such
structural ageing is compatible with the existence of a
velocity-weakening regime at velocities smaller than
, hence with
the existence of the healing instability.
46.50.+a - Fracture mechanics, fatigue and cracks.
46.55.+d - Tribology and mechanical contacts.
83.80.Rs - Rheology: Polymer solutions.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003
