Crack detection in a rotor dynamic system by vibration monitoring - Part I: Analysis

Many practical rotor dynamic systems contain shaft/rotor elements that are highly susceptible to transverse cross-sectional cracks due to fatigue. The early detection of mechanical malfunction that can be provided by an effective vibration monitoring system is essential. Two theoretical analyses, global and local asymmetry crack models, are utilized to identify 'characteristics of the system response that may be directly attributed to the presence of a transverse crack in a rotating shaft. A model consisting of an overhung whirling rotor is utilized to match an experimental test rig. A 2X harmonic component of the system response is shown to be the primary response characteristic resulting from the introduction of a crack. Once the unique characteristics of the system response are identified, they serve then as target observations for the monitoring system.