Fig. 2.

The transition wave can be initiated anywhere along the chain, with compressive and rarefaction pulses proceeding in opposite directions from the point of initiation (here $d=18.6$ mm). (A and B) The normalized displacements of the individual bistable elements (${\widehat{x}}_i$ for each of the i elements in the chain) during the propagation of the wave, as recorded with a high-speed camera at 500 Hz. These panels show the propagation of the transition with a constant velocity and pulse width, after a brief initiation period during which steady-state is established. (C and D) Optical images of the experiments during wave propagation (obtained from a high-speed camera), corresponding to the data in A and B. (E and F) Simulations corresponding to the experiments shown in A and B, showing excellent quantitative agreement. For the compression-initiated pulse, the initiating displacement of the wave takes place on the left of the chain and is in the same direction as the pulse propagation; for the tension-initiated pulse, the initiating displacement takes place on the right of the chain, and the local tensile displacement is in the opposite direction of the wave propagation.