Abstract
This paper deals with 1/2-order subharmonic oscillations in a nonlinear two-degree-of-freedom system where the natural frequencies are comparatively close. The first-order approximated equations of the subharmonic oscillations are derived by using the multiple time scales method. The results of the bifurcation analysis are then compared with the results of the numerical simulation of the original equations of motion. As a result, the approximate solutions of 1/2-order subharmonic oscillations bifurcate into combination resonance when the excitation frequency is close to the sum of the two natural frequencies. In addition, as the two natural frequencies get closer, the subharmonic oscillations may change to chaotic vibrations.
