Recent Advances in Vibration Based Damage Detection Techniques for Cracked Rotors

In recent years, there has been a growing interest in the development of structural health monitoring for rotating structures, and especially shaft crack detection methodologies and on-line diagnostic techniques. Crack initiated problems present a significant safety and loss hazard in nearly every application of modern turbomachinery, including aircraft engines and power generation units. Different approaches are used to model, sense, and localize crack-induced damage in rotating structures. This presentation will provide an overview of the recent progress in the vibration based health monitoring and rotor crack detection techniques developed by author in recent years. A brief review of the unique properties of rotating structures will be followed by remarks on application of modal and sensor norms for localization of damage and providing information concerning its impact on the structure’s natural modes of vibration. The transient response of a cracked flexible rotor passing through its critical speed will be presented for crack detection and monitoring, including the effect of the presence of a constant driving torque. Then, the coupling between lateral and torsional vibrations will be discussed for a rotor dynamic system with breathing crack model. This will be demonstrated analytically for the simple rotor model and with finite-element approach for more realistic cases. Finally, a concept on how crack detection technologies might be incorporated as part of an overall prognostic system for bladed-disk assemblies will be discussed