Improved Crack Closure Line Position: An Improved Model for Crack Breathing Phenomenon

R. Ramezanpour, M. Ghayour and S. Ziaei-Rad

International Journal of Acoustics and Vibration, Volume 20, Number 3, September 2015, Pages 123-134

ABSTRACT

The dynamic behaviour of a cracked Jeffcott rotor is investigated in this paper. The crack is located at the midpoint of the rotor. It is known that when the static deflection dominates the vibration of the rotating shaft, the crack opens and closes according to the shaft rotation. This phenomenon is known as crack breathing. There are several models for classifying crack breathing phenomena, such as the switching crack model, harmonic approach model, and response-dependent breathing crack model. In order to model the breathing of the crack in the response-dependent breathing crack model, the concept of a crack closure line position (CCLP) is proposed and used by some researchers. The main scope of this work is to present an improved crack closure line position (ICCLP). By using several contour plots over the crack's surface, it is shown that the imaginary line that separates the open and closed parts of a breathing crack should not be considered perpendicular to the crack tip. It is also shown that the improved model positively agrees with those proposed in the literature. The effects of ICCLP on the coefficients of the local flexibility matrix are investigated.