Application of triaxial force sensor to impact testing of spinning rotor systems

Impact testing is shown to be a practical method of verifying the speed-dependent dynamic characteristics of a rotating system. The method could also be applied to assess changes in a rotating machine's condition without interfering with scheduled operation. A pendulum-mounted multi-axis force sensor is used as an impact device to enable measurement of the tangential force component induced by friction. Complex modal analysis is applied to clearly distinguish forward and backward modes and separate them in the frequency domain. The fact that mixed whirl of a rigid rotor on anisotropic supports can be excited by rotating mass imbalance is demonstrated. Analytical developments are verified with experimental data obtained from a simply supported rigid rotor test rig with significant gyroscopic effects.