For fixed damping and fixed excited frequency the motion of the beam under small amplitude of force is periodic, but becomes chaotic through period doubling bifurcation with increase of the force.
The equivalent viscous damping ratio and the equivalent natural frequency are obtained by comparing the system with a purely linear, spring-mass-damper system of single freedom.
通过和单自由度线性弹簧-质量-阻尼系统进行比较，得到该带裂缝梁结构的等效自然频率和等效粘滞阻尼比。
3
The natural frequency, damping ratio and mode shape of a multi-degree-of-freedom system are analyzed and the identified results are in good agreement with the theoretical values.