A Fault Analysis Cracked-Rotor-to-Stator Rub and Unbalance by Vibration Analysis Technique

An analytical 4-DOF nonlinear model of a de Laval rotor-stator system based on Energy Principles has been used theoretically and experimentally to investigate fault symptoms in a rotating system. The faults, namely rotor-stator-rub, crack and unbalance are modeled as excitations on the rotor shaft. Mayes steering function is used to simulate the breathing behaviour of the crack. The fault analysis technique is based on waveform signal, orbits and Fast Fourier Transform (FFT) derived from simulated and real measured signals. Simulated and experimental results manifest considerable mutual resemblance of elliptic-shaped orbits and FFT for a same range of test data.

Authors:

• B. X. Tchomeni
• A. A. Alugongo
• L. M. Masu

Keywords:

• A breathing crack
• fault
• FFT
• nonlinear
• orbit
• rotorstator rub
• vibration analysis.

References:

[1] T. H. Patel, and A. K. Darpe, Coupled bending torsional vibration
analysis of rotor with rub and crack, Journal of Sound and Vibration
Vol. 326, 2009, pp 740–752.
[2] F. Chu, and W. Lu, Determination of the rubbing location in a multi-disc
rotor system by means of dynamic stiffness identification. Journal of
sound and vibration, 2001. 235-246.
[3] R. F. Beatty, Differentiating Rotor response due to radial rubbing,
Journal of Vibration, Acoustics, Stress, and Reliability in Design
Vol107, 1985, pp151–160.
[4] B. O. Al-bedoor, Transient torsional and lateral vibrations of unbalanced
rotors with rotor-to-stator rubbing. Journal of Sound and vibration
229(3), 2000, 627-645.
[5] J. T. Sawicki, J. Padovan, and R. Al-Khatib, The Dynamics of Rotor
with Rubbing. International Journal of Rotating Machinery 1999, Vol. 5,
No. 4, 1998, pp. 295-304.
[6] J. T. Sawicki, X. Wu, G. Y. Baaklini, and A. L. Gyekenyesi, “Vibrationbased
crack diagnosis in rotating shafts during acceleration through
resonance,” in Nondestructive Evaluation and Health Monitoring of
Aerospace Materials and Composites II, vol. 5046 of Proceedings of
SPIE, 2003, pp. 1–10, San Diego, Calif, USA.
[7] Y. B. Kim, and S. T. Noah, Bifurcation analysis for modified Jeffcott
rotor with bearing clearances, Nonlinear Dynamics Vol. 1, 1990, pp
221-241.
[8] F. Chu, and W. Lu, Stiffening effect of the rotor during the rotor-tostator
rub in a rotating machine, Journal of Sound and Vibration Vol.
308, 2007, pp 758–766.
[9] R. Sukkar, and A. S. Yigit, Analysis of fully coupled torsional and
lateral vibrations of unbalanced rotors subject to axial loads. Kuwait J.
Sci. Eng. 35 (2B), 2008, pp. 143-170.
[10] R. Gasch, A Survey of the Dynamic Behaviour of a Simple Rotating
Shaft with Transverse Crack, Journal of Sound and Vibration, 1993,
160(2): 313-332.
[11] B. Grabowski, The vibrational behavior of a turbine rotor containing a
transverse crack. ASME Design Engineering Technology Conference, St.
Louis, 1979. Paper No. 79-DET-67.
[12] J. J. Sinou, Condition Monitoring for Notched Rotors Through Transient
Signals and Wavelet Transform Experimental Mechanics 49 (2012) 683-
695.
[13] I. Mayes, and W. Davies, The vibration behavior of a rotating shaft
system containing a transverse crack. Vibration in rotating machinery,
Inst. Mech, E. 1976, p.53-65.
[14] B. X. Tchomeni, A. A. Alugongo, and L. M. Masu, In situ Modelling of
Lateral-Torsional Vibration of a Rotor-Stator with Multiple Parametric
Excitations. World Academy of Science, Engineering and Technology
International Journal of Mechanical, Aerospace, Industrial and
Mechatronics Engineering Vol:8 No:11, 2014.
[15] A. S. Yigit, and A. P. Christoforou, Coupled Torsional and Bending
Vibrations of Actively Controlled Drillstings. Journal of Sound and
Vibration, 2000, 234: 67-83.
[16] A, D. Dimarogonas, Vibration Engineering, West Publishers, St. Paul.
1976.
[17] A. K. Darpe, Dynamics of cracked rotor. PhD Thesis, IIT Delhi, 2000.