Vibration and energy characteristics of a rub-impact rotor with bending-torsion coupling

Abstract

Rotor-stator rub-impact is a recurrent and destructive secondary fault in modern aero-engines and gas turbines where radial clearances are continually reduced. Previous research has treated bending-torsion coupling and strain energy characteristics as separate problems, impeding a unified understanding of the underlying energy transfer mechanisms. This paper develops a unified bending-torsion coupled single-disk rotor model with nonlinear rub-impact forces and introduces strain energy theory to quantify the coupled vibration response. Numerical and experimental results reveal that the coupling establishes a unidirectional energy pathway from bending to torsional vibration, significantly amplifying the torsional response and generating characteristic 2 × harmonics and combination frequencies that emerge even prior to full annular rubbing, thereby establishing torsion as a highly sensitive early fault indicator. Structural parameters (eccentricity and clearance) modulate the coupling intensity indirectly through rub-impact severity, yielding approximately linear correlations with torsional amplitude. Moreover, the three-dimensional strain energy trajectory undergoes a distinct morphological evolution-from a smooth loop through a rough band to a dense energy surface-as rub-impact intensifies, providing an intuitive energy-domain criterion for identifying nonlinear state transitions. Experimental tests on a Bently RK4 rig confirm the model’s validity. This work offers an energy-based diagnostic paradigm that clarifies the central role of bending-torsion coupling in the fault dynamics of rotor systems.