The influence of crack-imbalance orientation and orbital evolution for an extended cracked Jeffcott rotor

Julio Gomez-Mancilla (1) , Jean-Jacques Sinou (2) , V.R. Nosov (1) , Fabrice Thouverez (2) , A. Zambrano (1)

1 Lab. Vibraciones & Rotodinamica ESIME
2 LTDS - Laboratoire de Tribologie et Dynamique des Systèmes

Vibration peaks occurring at rational fractions of the fundamental rotating critical speed, here named Local Resonances, facilitate cracked shaft detection during machine shut-down. A modified Jeffcott-rotor on journal bearings accounting for gravity effects and oscillating around nontrivial equilibrium points is employed. Modal parameter selection allows this linear model to represent first mode characteristics of real machines. Orbit evolution and vibration patterns are analyzed, yielding useful results. Crack detection results indicate that, instead of 1x and 2x components, analysis of the remaining local resonances should have priority; this is due to crack-residual imbalance interaction and to 2x multiple induced origins. Therefore, local resonances and orbital evolution around 1/2, 1/3 and 1/4 of the critical speed are emphasized for various crack-imbalance orientations.

Mots clés: Vibrations; Dynamic systems; Rotor dynamics; Crack detection; Local resonance; Extended Jeffcott rotor; Orbital evolution

Domaines: Vibrations [physics.class-ph]; Vibrations [physics.class-ph]; Mécanique des structures [physics.class-ph]; Mécanique des structures [physics.class-ph]

Julio Gomez-Mancilla, Jean-Jacques Sinou, V.R. Nosov, Fabrice Thouverez, A. Zambrano. The influence of crack-imbalance orientation and orbital evolution for an extended cracked Jeffcott rotor. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2004, 332 (12), pp.955-962. ⟨10.1016/j.crme.2004.09.007⟩. ⟨hal-00207642⟩