On the friction and adhesion hysteresis between polymer brushes attached to curved surfaces: Rate and solvation effects

Computer simulations of friction between polymer brushes are usually simplified compared to real systems in terms of solvents and geometry. In most simulations, the solvent is only implicit with infinite compressibility and zero inertia. In addition, the model geometries are parallel walls rather than curved or rough as in reality. In this work, we study the effects of these approximations and more generally the relevance of solvation on dissipation in polymer-brush systems by comparing simulations based on different solvation schemes. We find that the rate dependence of the energy loss during the collision of brush-bearing asperities can be different for explicit and implicit solvent. Moreover, the non-Newtonian rate dependences differ noticeably between normal and transverse motion, i.e., between head-on and off-center asperity collisions. Lastly, when the two opposing brushes are made immiscible, the friction is dramatically reduced compared to an undersaturated miscible polymer-brush system, irrespective of the sliding direction

Angular dependence of atomic friction with deformable substrate

The atomic stick-slip behavior of Prandtl-Tomlinson model sliding on 2D deformable substrate is studied. The influence of the shape of the interaction potential is investigated in details in the well-known phenomenon of the two-dimensional stick-slip friction. Numerical simulations are built to observe the influence of the geometry and orientation. The results show that the friction force has a maximum at r = − 0.6, this value of the shape parameter indicates a transition from a clear stick-slip at r> − 0.6 to a distorted stick-slip at r< − 0.6. We find a remarkable transition of the frictional force image pattern depending on the shape of the substrate

Nonlinear spring model for frictional stick-slip motion

Frictional stick-slip dynamics is discussed using a model of one oscillator pulled by a nonlinear spring force. We focus our attention on the nonlinear spring parameter k0. The dynamics of the model is carefully studied, both numerically and analytically. Our numerical investigation, which involves bifurcation diagrams, shows a rich spectrum of dynamical behavior including periodic, quasi-periodic and chaotic states. On the other hand, and for a good selection of parameters , the motion of the particle involves periodic stick-slip, erratic and intermittent motions, characterized by force fluctuations, and sliding. This study suggests that the transition between each of motion strongly depends on the nonlinear parameter k0. The system also displays resonance at fractional frequencies of the oscillator

Frictional stick-slip dynamics in a nonsinusoidal Remoissenet-Peyrard potential

Frictional stick-slip dynamics is studied theoretically and numerically in a model of one oscillator interacting with a nonsinosoidal subtracted potential. We focus our attention on a class of parameterised one-site Remoisenet-Peyrard potential U RP (X,r), whose shape can be varied as a function of parameter r and which has the sine-Gordon shape as the particular case. The dynamics of the model is carefully studied, both numerically and analytically. Our numerical investigation, which involves bifurcation diagrams, shows a rich spectrum of dynamical behavior including periodic, quasi-periodic and chaotic states. On the other hand, and for a good selection of the parameter systems, the motion of the particle involves periodic stick-slip, erratic and intermittent motions, characterized by force fluctuations, and sliding. This study suggests that the transition between each of motion strongly depends on the shape parameter r. However, the stick-slip phenomena can be observed for all values of the shape parameter r in the range |r|>1. The analytical analysis of the dry friction reveals that the dynamic depends non trivially on the shape parameter r, which shows the importance of deformable substrate potential in the description of real physical systems. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 200746.55.+d Tribology and mechanical contacts, 68.35.Iv Acoustical properties, 81.40.Pq Friction, lubrication, and wear,

Nonlinear spring model for frictional stick-slip motion

46.55.+d Tribology and mechanical contacts, 68.35.Gy Mechanical properties; surface strains, 81.40.Pq Friction, lubrication, and wear,