Damage detection in rotating shafts possessing transverse crack through vibration analysis of breathing crack model

Subject Areas : Modal Analysis

Abbas Azemati ¹ , Mehdi Salehi ² , Sattar Mohammadi-Esferjani ³

1 - Department of Mechanical Engineering, Islamic Azad University, Najafabad Branch, Najafabad, Iran
2 - department of mechanical engineering, Islamic Azad University of Najafabad
3 - Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

Received: 2018-10-23 Accepted : 2018-12-20 Published : 2019-02-20

Keywords: Vibration, Damage Detection, Rotating Shaft, Breathing Crack,

Abstract :

This paper deals with transverse crack identification in rotating shafts. In this research, after presenting the equations governing the problem, different depths and positions of crack in a rotating axis of an industrial compressor unit is investigated using a breathing crack model. Crack is modeled based on the principles of fracture mechanics and the system's motion equations are extracted. Stress intensity coefficients are implemented to model the actual crack behavior in gradual opening and closeing situations. The results showed that in the points where the cracks are closed, the stiffness has its maximum value. Also, with increasing crack depth, the total stiffness of the shaft decreases. The first harmonic in the frequency corresponds to imnbalance and the second harmonic associated with the crack effect. By changing the position of the crack from the ends to the center of the shaft, the frequency of the second harmonic decreases while its amplitude decreases. Inverse analysis can be carried out based on the second frequency along with its amplitude in order to crack identification.