Vibration analysis and experiment on transmission system of a rotor test rig

Transfer Matrix Method(TMM) was used to analyze the vibration characteristics of a helicopter test rig. The torsional vibration natural frequencies and the modal shapes were obtained. Each order natural frequency and the relationship between the lateral vibration and support stiffness of the test rig transmission were obtained. By experiment, vibrations in three directions were measured. After the rotor runs over the resonance of the test rig at a speed of 960 r/min, the test rig will run in a steady state for about 2~3 seconds and then the vibration goes to diverge. The frequency of the spindle speed leading to vibration divergence is just right the 1st order natural frequency of the lateral vibration. Based on the vibration analysis, it is concluded that the vibration divergence is related to the support stiffness of the transmission. Two methods for dealing with this malfunction were given.