Summary
This paper deals with the parametric stiffness excitation of an unconstrained dynamical system with three degrees of freedom. A constant force at the first degree of freedom drives the system, and both mass- and stiffness-proportional damping are considered. The parametrically excited vibrations are studied numerically by using fourth-order Runge-Kutta method. Amplitudes of the stationary (steady state) difference vibrations show resonances at both the second and third eigenfrequency of the structure. Floquet theory is employed for a numerical stability analysis. Large instability regions appear at fundamental parametric resonance frequencies of first order and at a parametric combination frequency of first order.
