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Transient Response of Rotor on Rolling Element Bearings with Clearance

David P. Fleming, Brian T. Murphy, Jerzy T. Sawicki & J. V. Poplawsk
NASA Glenn Research Center Cleveland, OH 44135, USA
Published: August, 28 2013

Abstract


Internal clearance in rolling element bearings is usually present to allow for radial and axial growth of the rotor-bearing system and to accommodate bearing fit-up. The presence of this clearance also introduces a “dead band” into the load-deflection behavior of the bearing. Previous studies demonstrated that the presence of dead band clearance might have a significant effect on synchronous rotor response. In this work, the authors investigate transient response of a rotor supported on rolling element bearings with internal clearance. In addition, the stiffness of the bearings varies non linearly with bearing deflection and with speed. Bearing properties were accurately calculated with a state of the art rolling bearing analysis code. The subsequent rotor dynamics analysis shows that for rapid acceleration rates the maximum response amplitude may be less than predicted by steady-state analysis. The presence of clearance may shift the critical speed location to lower speed values. The rot or vibration response exhibits sub harmonic components which are more prominent with bearing clearance.

Full Text (Pdf)

Bearing clearance, Transient response, Rotordynamics, Rolling-element bearing stiffness, Dynamic analysis, Speed ramp analysis.


Internal clearance in rolling element bearings is usually present to allow for radial and axial growth of the rotor-bearing system and to accommodate bearing fit-up. The presence of this clearance also introduces a “dead band” into the load-deflection behavior of the bearing. Previous studies demonstrated that the presence of dead band clearance might have a significant effect on synchronous rotor response. In this work, the authors investigate transient response of a rotor supported on rolling element bearings with internal clearance. In addition, the stiffness of the bearings varies non linearly with bearing deflection and with speed. Bearing properties were accurately calculated with a state of the art rolling bearing analysis code. The subsequent rotor dynamics analysis shows that for rapid acceleration rates the maximum response amplitude may be less than predicted by steady-state analysis. The presence of clearance may shift the critical speed location to lower speed values. The rot or vibration response exhibits sub harmonic components which are more prominent with bearing clearance.