Abstract:

The vibration equations and boundary conditions are established from the energy function of a beam system which is suspended with ropes; subsequently, the natural frequency characteristics equation is acquired. It is demonstrated that the free-free boundary model is the degenerated condition of the beam system. By solving this characteristics equation numerically, the natural frequency and modal relative to the length or density of the suspension rope is obtained. The appearance of the multiple first-order modals in a certain rocket’s modal test is explained by using this method.

Key words: Rocket, Modal, Free free boundary, Suspension rope, Suspended beam