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Breakloose suppression in minimal friction models

Shubham Agarwal

Abstract

Breakloose friction, the transient force peak at the onset of sliding, is often pronounced in nanoscale contacts but weak or absent in macroscopic systems. Although this behavior is commonly associated with rupture fronts and process-zone effects, how the stiction peak is controlled by system size, temperature, driving rate, and loading geometry, and what mechanisms underlie its emergence or suppression, remains incompletely understood. Here we investigate this problem using three minimal friction models with distinct loading geometries: a multi-particle Prandtl-Tomlinson system with independently driven particles, an end-driven Frenkel-Kontorova chain with elastic stress transmission along the interface, and a uniformly driven FK chain in which each site is coupled locally to the driving stage. We show that similar macroscopic suppression of breakloose friction can arise from fundamentally different mechanisms. In multi-particle PT systems, increasing system size or temperature promotes statistical dephasing of local depinning events, smoothing the global response. In end-driven FK chains, internal elasticity redistributes stress along the interface, delaying sliding onset and, together with higher temperature or slower driving, enabling progressive relaxation during loading. In uniformly-driven FK chains, the stiffness of the driving springs controls the synchronization of slip events and thereby the character of the sliding response. These results demonstrate that the presence or absence of a breakloose peak does not uniquely identify a single physical mechanism, but instead reflects the interplay of local pinning, elastic coupling, and contact architecture.

Breakloose suppression in minimal friction models

Abstract

Breakloose friction, the transient force peak at the onset of sliding, is often pronounced in nanoscale contacts but weak or absent in macroscopic systems. Although this behavior is commonly associated with rupture fronts and process-zone effects, how the stiction peak is controlled by system size, temperature, driving rate, and loading geometry, and what mechanisms underlie its emergence or suppression, remains incompletely understood. Here we investigate this problem using three minimal friction models with distinct loading geometries: a multi-particle Prandtl-Tomlinson system with independently driven particles, an end-driven Frenkel-Kontorova chain with elastic stress transmission along the interface, and a uniformly driven FK chain in which each site is coupled locally to the driving stage. We show that similar macroscopic suppression of breakloose friction can arise from fundamentally different mechanisms. In multi-particle PT systems, increasing system size or temperature promotes statistical dephasing of local depinning events, smoothing the global response. In end-driven FK chains, internal elasticity redistributes stress along the interface, delaying sliding onset and, together with higher temperature or slower driving, enabling progressive relaxation during loading. In uniformly-driven FK chains, the stiffness of the driving springs controls the synchronization of slip events and thereby the character of the sliding response. These results demonstrate that the presence or absence of a breakloose peak does not uniquely identify a single physical mechanism, but instead reflects the interplay of local pinning, elastic coupling, and contact architecture.
Paper Structure (10 sections, 3 equations, 10 figures)

This paper contains 10 sections, 3 equations, 10 figures.

Table of Contents

  1. Introduction
  2. Model and methods
  3. Prandtl-Tomlinson model
  4. Frenkel-Kontorova model
  5. Results
  6. Prandtl-Tomlinson model
  7. End-driven Frenkel-Kontorova chain
  8. Uniformly-driven Frenkel-Kontorova chain
  9. Conclusions
  10. MPPT: Driving-rate effect

Figures (10)

  • Figure 1: Schematics showing (a) a multi-particle Prandtl-Tomlinson model; (b) an end-driven FK chain; (c) a uniformly-driven FK chain.
  • Figure 2: The effect of temperature for a MPPT model with 128 atoms on (Left) force trace, and (Right) stiction peak magnitude.
  • Figure 3: (Left) The effect of system-size on force trace per particle for a 1D-PT model at $k_BT/V_0=0.1$; (Right) The standard deviation in force-per-particle at macroscopic stiction peak as a function of system size.
  • Figure 4: (Left) The effect of temperature on the evolution of friction-force per particle for periodic 1D-FK chain; (Right) The variation of stiction peak magnitude ($\Delta F$) with temperature for periodic and open chains. Chain is end-driven with soft spring ($k/k_{\text{bond}}=0.1$) at $v=1\times 10^{-3}$.
  • Figure 5: The effect of chain length on friction-force per particle for an end-driven 1D-FK chain with periodic (left) and open (right) boundary conditions. End particle of FK-chain is pulled by a soft spring ($k_{\text{drive}}/k_{\text{spring}}=0.1$) at $v=1\times 10^{-2}$.
  • ...and 5 more figures