On the walking stick–slip problem

• Fiber pullout tests show stick–skip; the fiber exits the fixture in discrete steps.
• A translational dynamic model accurately predicts the stick–slip oscillation period.
• A model with rotations predicts the stick–slip phase of the two contact interfaces.

The friction-excited dynamics of a two-sided interface are examined experimentally, and complementary modeling and simulation efforts are used to understand the experimental observations. The experiment uses a thin fiber pulled from between two clamping pads. The experiment shows that stick–slip behaviors of the two clamping pads are periodic but out of phase, a behavior dubbed “walking stick–slip”, because the pullout specimen pulls out of the fixture in discrete, alternating steps. The friction behavior is understood using two dynamic models: (i) a three degree-of-freedom translational model, and (ii) a model augmented with rotational degrees-of-freedom. The out-of-phase walking arises from the component rotations. “Walking” stick–slip (to our knowledge) is a previously unreported phenomenon which may have implications in a variety of other situations.