Eventos Anais de eventos
DINAME 2017
XVII International Symposium on Dynamic Problems of Mechanics
ANALYSIS OF THE DYNAMIC BEHAVIOR OF A CRACKED ROTATING SHAFT BY USING THE HARMONIC BALANCE APPROACH
Submission Author:
Aldemir Ap Cavalini Jr , MG , Brazil
Co-Authors:
Aldemir Ap Cavalini Jr, Tobias Morais, Nicolò Bachschmid, Valder Steffen Jr
Presenter: Aldemir Ap Cavalini Jr
doi://10.26678/ABCM.DINAME2017.DIN17-0178
Abstract
There are several SHM techniques proposed in the literature for crack detection in rotating machines. Among them, the ones based on vibration measurements are recognized as useful tools in the industrial context. Although widely used, when applied under non-ideal conditions, such techniques can only detect cracks that eventually have already spread significantly along the cross section of the shaft (usually above 40% of its diameter). Therefore, currently, the researchers' attention is turning to more sophisticated methods capable of identifying incipient cracks (cracks that spread up to 25% of shaft diameter), which represent a type of damage that are hardly observable in classical vibration analysis. In a previous contribution, a crack identification methodology based on a nonlinear approach was proposed. The technique uses external applied diagnostic forces at certain frequencies attaining combinational resonances, together with a pseudo-random optimization code, known as Differential Evolution, in order to characterize the signatures of the crack in the spectral responses of flexible rotor. In the present paper, the favorable conditions to apply the proposed methodology are investigated. The analysis procedure is confined to the operating parameters of the system, being characterized by the rotation speed of the rotor and the amplitude and frequency of the diagnostic forces. The harmonic balance approach is used to determine the vibration responses of the cracked rotor system and the open crack behavior is simulated according to the FLEX model. For illustration purposes, a rotor composed by a horizontal flexible shaft, two rigid discs, and two self-aligning ball bearings is used to compose a FE model of the system.
Keywords
Rotordynamics, crack identification, harmonic balance approach, FLEX model, crack detection
