The effect of a geometry-based breathing crack model on a viscoelastic composite rotor-shaft system

This study investigates the role of a breathing crack on a viscoelastic composite rotor-shaft system supported at the ends by journal bearings. A finite element-based mathematical formulation is developed to model the breathing crack. The geometry of the crack configuration is used to derive a time-dependent stiffness matrix. This matrix is then incorporated into the equation of motion for the composite shaft, derived with the Equivalent Modulus Theory (EMT). The equation of motion is of higher order due to the inclusion of the material's internal damping behavior, modeled using an operator-based viscoelastic model. Upon validating the mathematical model of the breathing crack, we analyzed its effects over one complete shaft rotation. This analysis further compared the strain energy and orbit plots of the cracked shaft with those of an intact shaft.