Abstract
Nonlinear characteristics of two DOF Duffing oscillator are investigated. In our previous study, mass and stiffness proportional dampings were used separately, and the nonlinear characteristics appeared only near the first and second resonance frequency, respectively. To investigate nonlinear properties of both natural frequencies, the case that mass and stiffness proportional dampings exist simultaneously is considered. Two combinations of stiffnesses that have same natural frequencies are used. The frequency response curves calculated by harmonic balance method show that the nonlinear characteristics moves from the first resonance frequency to the second one as the mass proportional damping increases. The frequency response curves of the elongations of springs are also considered. For the system that has the same stiffness characteristics for both springs, the larger deformed spring is changed by the order of the natural frequency.However, for the system that has the different stiffness characteristics, the larger deformed spring is unchanged.
