Transition to chaos in the Duffing oscillator

Abstract
It is observed in the Duffing oscillator that a bifurcation from a solution composed of only odd harmonics to one composed of both even and odd harmonics precedes the period-doubling bifurcations. Keeping all parameters fixed except for the amplitude of the driving force F, we determine the value of F at which the bifurcation occurs. Results are compared with experiment. A mechanism for the period-doubling bifurcations is suggested.