05-04: Natural Frequency Characteristics of Drive Shafts

For rotating machinery utilizing drive shafts, it is important to operate at a speed sufficiently lower than the drive shaft's natural frequency to prevent destructive vibration. In this paper, the theory of determining the shaft's natural frequency is presented as well as methods for empirically testing a shaft's natural frequency. Vibrations levels in the region of the natural frequency are empirically determined for composite drive shafts and multiple test methods for determining the natural frequency are described and compared. The effect of the end conditions is discussed and an appropriate end condition is presented, and finally, the effect on natural frequency when a torque is applied to the composite shaft if presented.