TORSIONAL VIBRATION ANALYSIS FOR A HELICOPTER TRANSMISSION SYSTEM

In order to obtain the characteristics of the torsional vibration of a helicopter transmission system, a calculation of the torsional vibration is carried out. The transmission system is divided into the subsystems of shaft segment and disks, based on a simplified structure of the transmission system. The solution of the torsional vibration can be obtained using the modal superposition method. The torsional frequency response function of a helicopter transmission system is analyzed. The result shows that there is the extreme value of amplitude of a torsional frequency response function near low order torsional nature frequencies. When the same order torsional resonance is produced in a helicopter transmission system by excitation parts with different frequencies, the rotation speed of an engine is unequal. The larger transmission ratio from an engine to excitation parts is, the higher rotation speed of an engine is. When torsional resonance of a transmission system is caused by a rotor, the rotation speed of an engine is the largest in the same order torsional resonance.