Vibration-Based Techniques for Damage Detection and Health Monitoring of Mechanical Systems

The state of the art in vibration-based damage detection and health and usage monitoring is reviewed. The damage detection concepts and the signal analysis techniques are examined, explained, and compared. Latest advances in signal processing methodologies that are of relevance to vibration based damage detection (e.g., Wavelet Transform and Wigner-Ville distribution) are highlighted. These vibration signalprocessing methods play an important role in early identification of incipient damage that can later develop in a potential threat to the system functionality. A brief mathematical description of the techniques for vibration-based damage detection/health monitoring in rotating mechanical systems is given. Technologies for vibration reduction of rotating machinery as well as current Health and Usage Monitoring Systems (HUMS) programs installed on the civil and military helicopters are reviewed. The current procedures for Rotor Track and Balance (RT&B) of the helicopters are explained and vibration data from the sensors mounted in the cockpit showing the reduction in vertical vibrations are presented. HUMS instrumentation and technologies are briefly examined. To illustrate these issues on a tractable example, the damage detection of a cracked specimen was investigated. The non-linear equations of motions were set up and damage was simulated as a change in the stiffness of the specimen. The relative crack size considered in this study was r = 0 (pristine case) r = 0.1 (small crack), r = 0.4 (medium crack), and r = 0.6 (large crack). Using MATLAB-SIMULINK software, the