Nonlinear friction dynamics on polymer surface under accelerated movement

Abstract

Nonlinear phenomena on the soft material surface are one of the most exciting topics of chemical physics. However, only a few reports exist on the friction phenomena under accelerated movement, because friction between two solid surfaces is considered a linear phenomenon in many cases. We aim to investigate how nonlinear accelerated motion affects friction on solid surfaces. In the present study, we evaluate the frictional forces between two polytetrafluoroethylene (PTFE) resins using an advanced friction evaluation system. On PTFE surfaces, the normalized delay time δ, which is the time lag in the response of the friction force to the accelerated movement, is observed in the pre-sliding friction process. Under high-velocity conditions, kinetic friction increases with velocity. Based on these experimental results, we propose a two-phase nonlinear model including a pre-sliding process (from the beginning of sliding of a contact probe to the establishment of static friction) and a kinetic friction process. The present model consists of several factors including velocity, acceleration, stiffness, viscosity, and vertical force. The findings reflecting the viscoelastic properties of soft material is useful for various fields such as in the fabrication of clothes, cosmetics, automotive materials, and virtual reality systems as well as for understanding friction phenomena on soft material surfaces.

Friction Dynamics on Rough Agar Gel Surfaces

“…At an angular velocity of 0.01 rad s 1 and normal force of 0.98 N, an asymmetric small peak was observed at a sliding velocity of V 0.03 mm s 1 in outward pre-sliding process. Such peaks and steps have been observed on flat agar gel and polytetrafluoroethylene surfaces 19,24,25 . Static friction with a friction coefficient of 0.36 was observed at V 0.04 mm s 1 .…”

“…Using the sinusoidal motion friction evaluation system, we evaluated the friction force between two fractal agar gel substrates in deionized water Fig. 1 19,24,25 . A detailed procedure of the evaluation method is described in the reference 19.…”

“…This decrease in δ with an increase in the ω can be attributed to the viscoelasticity of the gel and the thickness of the water film at the interface. The viscoelastic material behaves elastically against momentarily changing forces and behaves viscously against slowly changing forces 24,26 . At low velocity, the gel deforms along with sliding motion, which occurs the time lag to break the adhesion site and increases δ.…”

Tactile Texture of Cosmetic Sponges and Their Friction Behavior under Accelerated Movement

“…Each evaluation was conducted three times to confirm the repeatability. Figure 3 shows the sinusoidal motion-friction evaluation system 11,12 . Sinusoidal motion was achieved through the Scotch-yoke mechanism, in which the rotational movement of an eccentric disk is converted into sinusoidal reciprocating movement of a contact probe.…”

“…Nonlinear phenomena that cannot be described by the Coulomb-Amonton s law F μW F: friction force, W: vertical force, μ: friction coefficient can occur under such a complex motion. Recently, we developed a friction evaluation system where the speed varies sinusoidally with time to mimic the sliding behavior during cosmetic processes 11 .…”