Stick slip dynamics

Foam rheology has been a challenging area of research of interest for the yield behavior and stick-slip flow behavior (see the review by Kraynik [229]). Recent studies by Durian and co-workers combine simulations [230] and a dynamic light scattering technique suited to turbid systems [231], diffusing wave spectroscopy (DWS), to characterize coarsening and shear-induced rearrangements in foams. The dynamics follow stick-slip behavior similar to that found in earthquake faults and friction (see Section XU-2D). 

Yoshizawa FI, McGuiggan P and Israelaohvili J N 1993 Identification of a second dynamic state during stick-slip motion Science 259 1305-8... 

Mishin, Y., Suzuki, A., Uberuaga, B.P., Voter, A.F. Stick-slip behavior of grain boundaries studied by accelerated molecular dynamics. Phys. Rev. B 2007, 75, 224101-1-7. 

The frictional properties of PTFE arc unique Its unusually low static coefficient of friction decreases with increasing load and is lower than the dynamic coefficient of friction. This precludes stick-slip behavior. The low surface energy also prevents wetting by liquids other than low-surface-tension fluids like fluorocarbons. 

To avoid stick-slip, one should try to make the spring constant high enough (using stiff materials and stable constructions). It can be shown, that stick-slip may also arise from the velocity dependence of the friction coefficient [460], When the friction coefficient decreases with sliding velocity, stick-slip is amplified. When the friction coefficient increases with velocity, stick-slip is damped out. The former is usually the case at low speeds, certainly for the transition from static to dynamic friction, whereas the latter prevails usually at high velocity. 

F. Heslot, T. Baumberger, B. Caroli, and C Caroli, Creep, Stick-slip and Dry Friction Dynamics Experiments and a Heuristic Model, Phys. Rev., E49, 4973 (1994). 

We discuss the various dynamical models of earthquake-like failures in Chapter 4. Specifically, the properties of the Burridge-Knopoff stick-slip model (Burridge and Knopoff 1967) and of the self-organised criticality models, the Guttenberg-Richter type power laws, for the frequency distribution of earthquakes in these models are discussed here. 

The dynamics of shding systems can be very complex and depend on many factors, including the types of metastable states in the system, the times needed to transform between states, and the mechanical properties of the device that imposes the stress. At high rates or stresses, systems usually slide smoothly. At low rates the motion often becomes intermittent, with the system alternately sticking and slipping forward [31,44]. Everyday examples of such stick slip motion include the squeak of hinges and the music of violins. 

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