Cracked Rotors | Dr Anoop Chawla

Projects of the Simulation & Control Group (A. Chawla & S. Mukherjee)

Cracked Rotors

Dynamic response analysis of a cracked rotor is attempted. A response dependent breathing crack model accounts for the breathing of crack. Transient response and breathing behaviour of an accelerating / decelerating cracked rotor through sub harmonic resonances is studied using time domain, frequency domain and orbit plots.

The coupled vibrations of a cracked rotor are investigated using a response dependent breathing crack model. Initially a simple Jeffcott rotor is analysed considering the longitudinal and lateral vibrations. Additional external excitation in the form of periodic axial impulses is applied and the lateral vibration response in analysed. Later, to study all the coupling mechanisms together, the stiffness matrix of a Timoshenko beam element is modified accounting for bending-longitudinal-torsional vibration coupling mechanisms of crack. Using the breathing crack model and the FE model of the cracked rotor, the response of the cracked rotor is analysed applying external excitation. The excitation frequency in one mode is tuned to the natural frequency of vibration in the other mode, so as to excite resonance conditions. The interaction of the excitation frequencies with the rotational frequency and its harmonics is the focus of the study.

A mathematical model for a two-crack rotor is developed. The stiffness of the two-crack rotor is derived and then the dynamic response analysis is carried out to find the influence of crack orientation angle on the breathing behaviour of the cracks and on the response of the rotor. The dynamic response of an asymmetric rotor is then attempted to investigate the influence of an additional crack and its orientation on the rotor response. The effect of bow is incorporated in the equations of motion of the cracked rotor and its influence on the response of the rotor is also studied.

Finally, experimental investigations of some of the key findings of the analytical work are attempted. Peak response variation, time domain, frequency domain and orbit plot during the passage through sub harmonic resonances and coupled longitudinal and bending vibration response of cracked rotor are verified.

People Involved:

Faculties:

1.    Prof A Darpe

2.    Prof K Gupta

3.    Dr. A. Chawla

Students and Staff:

List of Sponsored Projects:

Related Publication:

1. Darpe AK, Gupta K, Chawla A, Coupled bending, longitudinal and torsional vibrations of a cracked rotor, JOURNAL OF SOUND AND VIBRATION 269 (1-2): 33-60 JAN 6 2004

2. Darpe AK, Gupta K, Chawla A, Transient response and breathing behaviour of a cracked Jeffcott rotor, JOURNAL OF SOUND AND VIBRATION 272 (1-2): 207-243 APR 22 2004

3. AK Darpe, A Chawla and K Gupta, Analysis of the response of a cracked Jeffcott rotor to axial excitation, Vol 249 No 3, Journal of Sound and Vibration, 2002.

4. A.K.Darpe, K.Gupta and A.Chawla, Experimental Investigation of the response of a cracked rotor to periodic axial excitation, Journal of Sound and Vibration, Vol 260 (2003), p 265-286.

5. A.K.Darpe, K.Gupta and A.Chawla, Dynamics of a two crack rotor, Journal of Sound and Vibration, Vol 259, No 3, 2003 pp 649-675.

6. Darpe A, Gupta K and Chawla A, Response of a rotor with an unstable propagating crack, Proceedings of Implast 2003.

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