The equations of motion of a rigid rotor mounted at both ends in discontinuously non-linear supports and subject to excitation by arbitrary imbalance are presented. The methods used to solve the equations are described briefly and the responses obtained from the model and an experimental rig are discussed and compared. Good correlation is found. Over a range of shaft speed the presence of aperiodic responses characterized by spectral sidebands which diverge with increasing shaft speed is noted. An explanation of the mechanism generating these sidebands is advanced.
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