Model-Based Crack Identification Using Full-Spectrum

This paper illustrates the application of full-spectrum technique for model-based identification of the crack and unbalance multi-fault parameters in cracked rotor systems. The rotor model chosen is a Laval rotor with disc unbalance and transverse surface crack. The crack force model is a switching crack, which has harmonic components exciting the rotor both in the same and reverse directions of the rotor spin. Development of identification algorithm uses linearized equations of motion in frequency domain. Full-spectrum obtains the complex Fourier coefficients of the force as well as the response. Further usage of these coefficients in the identification algorithm estimates the viscous damping, disc eccentricity, and additive crack stiffness as fault parameters. The accuracy of estimates increases on considering measurements at multiple spin speeds. The algorithm tests reasonably robust for various levels of measurement noise and bias errors in system parameters.