Micro-slip as a loss of determinacy in dry-friction oscillators

S. Webber, M. R. Jeffrey*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

2 Citations (Scopus)
86 Downloads (Pure)


Dry-friction contacts in mechanical oscillators can be modeled using nonsmooth differential equations, and recent advances in dynamical theory are providing new insights into the stability and uniqueness of such oscillators. A classic model is that of spring-coupled masses undergoing stick-slip motion on a rough surface. Here, we present a phenomenon in which multiple masses transition from stick to slip almost simultaneously, but suffer a brief loss of determinacy in the process. The system evolution becomes many-valued, but quickly collapses back down to an infinitesimal set of outcomes, a sort of "micro-indeterminacy". Though fleeting, the loss of determinacy means masses may each undergo different microscopic sequences of slipping events, before all masses ultimately slip. The microscopic loss of determinacy is visible in local changes in friction forces, and in creating a bistability of global stick-slip oscillations. If friction forces are coupled between the oscillators then the effect is more severe, as solutions are compressed instead onto two (or more) macroscopically different outcomes.

Original languageEnglish
Article number1930015
Number of pages21
JournalInternational Journal of Bifurcation and Chaos
Issue number6
Publication statusPublished - 15 Jun 2019


  • bifurcation
  • chaos
  • Discontinuity
  • friction
  • oscillators
  • sliding
  • slip
  • sticking
  • switching


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