Breathing mechanism of a cracked rotor subject to non-trivial mass unbalance

The effects of dynamic loading on crack breathing mechanisms are not yet thoroughly examined in literature. This paper introduces a parameter relating crack direction to bending load direction in order to model breathing behaviour of fatigue cracks subject to mass unbalance. Crack states (open, partial and closed) for shafts subject to weight-to-unbalance force ratios of 0.5, 1 and 2 and unbalance orientation angles of 0°, 45°, 90°, 135° and 180° were sometimes seen to be non-sequential or unchanging at particular crack depths. Additionally, the effects of varying unbalance angles and crack depth ratios on breathing mechanisms were also examined. An area moment of inertia method was used to develop a time-varying global stiffness matrix for each case and the results were found to be highly agreeable with the crack breathing behaviour in each case.