EXPERIMENTAL-EVIDENCE OF QUASI-PERIODICITY AND ITS BREAKDOWN IN THE COLUMN-PENDULUM OSCILLATOR

A new vibration absorbing device is introduced for large flexible stru ctures. The phase-space of the experimental system is reconstructed vi a delay-coordinate embedding technique. Experimental dynamics indicate that the motion is predominantly quasiperiodic, confirming the existe nce of invariant tori. Within the quasiperiodic region, there are wind ows containing intricate webs of phase-locked periodic responses. The quasiperiodic and the phase-locked responses are clearly visualized on the cover of the torus. Increase in the amplitude of excitation resul ts in distortion of the invariant torus due to the resonance overlap. Due to the resonance overlap, the return map extracted from the experi mental data becomes noninvertible. Furthermore, a burst of frequencies appears on the Fourier spectrum This scenario is similar to many expe rimental observations of hydrodynamical instabilities; the breakup of the tori in these experiments is related to the onset of turbulence.