Rotating machinery, which plays an important role in modern industries, is in extensive range of mechanical applications such as steam and gas turbines, air craft and automobile engines, pumps and even domestic applications. In the rotating machinery shaft one of the most serious damages is crack, and catastrophic failures and dangerous accidents may occur from cracks in aircraft engines and other rotating machinery. A very rich amount of literature about cracked rotors has appeared in the last four decades.
A lot of researches were conducted on cracked general shafts, but few studies of the modeling of hollow shafts with cracks were found. Most studies used classical models in modeling the crack breathing in hollow shafts.
Yang Hyong Ju, a researcher at the Faculty of Mechanical Science and Technology, has studied the actual breathing mechanism of a hollow shaft and presented generalized breathing functions of cracks. On the basis of it, he formulated an exact time-varying stiffness matrix of cracked elements and derived a finite element model of a rotor system. Then, he employed HBM to find the response, orbits and critical and subcritical speeds of a cracked rotor system. Finally, he analyzed the nonlinear vibration of a rotor system and compared the results with some published results, considering the eccentricity of disk, dimensionless crack depth, ratio of the inner radius to the outer radius of the rotor and angle between the crack and imbalance directions.
The results showed that the proposed generalized functions are more accurate than classical models, and they are superior to the functions introduced in previous studies in terms of generality.
If further information is needed, you can refer to his paper “Generalized breathing functions for stiffness model of transversely cracked hollow shaft” in “International Journal of Structural Stability and Dynamics” (SCI).
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