Experimental Characterisation of Asynchronous Partially Contacting Motion in a Multiple-Degree-of-Freedom Rotor System
RS Crespo, AD Shaw, MI Friswell (Swansea University) & AR Champneys (University of Bristol)
Mechanical Systems and Signal Processing, Vol. 145, November-December 2020, paper 106904
Recent theory has predicted the onset of asynchronous bouncing motion at speeds beyond those of internal resonance in multi-degree-of-freedom rotating systems with intermittent contact. This paper provides the first attempt to experimentally validate the theory. Vibrations incorporating rotor-stator contact are recorded from a vertically mounted rotordynamics test rig comprising two rigid shaft-disk assemblies that are axially joined by a bellows coupling. The upper rotor has an elastic bearing whereas the lower one is free but has a snubber ring located on its lower shaft, with clearance about 2.5% of the entire system's length. Nonlinear vibrations are excited by a small measured eccentricity of about 20% of the clearance. Measurements are taken by a wireless accelerometer and processed to produce an experimental bifurcation diagram, for small steps in the rotor speed, allowing the transients to decay. Evidence is found of bistability between quiescent and violent motion over a wide range of rotational speeds, including those representing both fundamental and internal resonances. The results are shown to qualitatively match numerical simulations from a differential equation model that incorporates rigid impacts.
This material has been published in Mechanical Systems and Signal Processing, Vol. 145, November-December 2020, paper 106904. The paper is published open access.
Link to paper using doi: 10.1016/j.ymssp.2020.106904
Mechanical Systems and Signal Processing on ScienceDirect