SNAPPING TORSIONAL RESPONSE OF AN ANISOTROPIC RADIALLY LOADED ROTOR

A rotor system with two orthogonal lateral and two angular (torsional) degrees of freedom is considered. The rotor has asymmetry of the late ral stiffness and is laterally loaded with a constant radial force and a rotating unbalance. Constant driving and load torques are applied t o the rotor. The important part of the research includes an analysis o f ''snapping'' action, when, during rotation, the rotor experiences a peak of torsional acceleration. This occurs when the ''strong stiffnes s'' axis of the anisotropic rotor passes under the axis of the sideloa d. The numerical simulation of the analytical model exhibits a snappin g (accelerated) torsional response of the rotor at twice synchronous f requency (2x), and it is especially pronounced at IX and 2X torsional resonances. The snapping response can initiate a rotor crack in the ar ea of stress concentration, can stimulate existing crack propagation, and can be a cause of the coupling failure. The analytical results are obtained by the Averaging Method application. They confirm the numeri cal results and show the possibility of combination resonance occurren ces. The synchronous dynamic stiffness for the frequency range around IX lateral resonance is analytically obtained The specific shape of th e quadrature dynamic stiffness component can serve as a shaft crack in dicator and can be used for early detection of a lateral crack on the rotor.