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.