Regarding machinery vibration, a mode is a natural frequency of a system. A rotor mode is a system mode where the rotor is the part of the system that is the dominant influence on the vibration response. The current paper reviews rotor modes for several rotor arrangements simulated on a rotor kit and modeled in a rotor dynamic code, XLTRC2. The rotor arrangements tested and modeled are (1) symmetrical rotor mass between bearings, (2) single overhung mass, and (3) two overhung masses. The paper discusses the concepts of modal superposition and modal participation in relation to the modeled and observed responses.

Michael J. Titone, P.E. is presently a Machinery Diagnostic Services Technical Leader for Bently Nevada. He joined the company in 2011. In prior job assignments, he worked for a power generation company and a vibration consulting firm in various roles. Since 1989, Michael has been a practicing engineer in the areas of vibration analysis, balancing, predictive maintenance/monitoring, mechanical system design/analysis, and I&C system design.

Michael earned a BS in mechanical engineering from Louisiana Tech University and an MBA from Mississippi College. He also earned 18 hours of graduate credit in mechanical engineering classes. He is a licensed professional engineer in the state of Mississippi and certified as a Category III Vibration Analyst through the Vibration Institute.