Vibrations of Cracked Rotors

Abstract

The analysis of dynamic behavior of rotors with cracks is considerably important for design aspect. In this study the effect of a single open crack on the free vibrational characteristics of a simply supported shaft are investigated using Finite element methodology. The rotor is modelled by using Timoshenko beam element. To account for the presence of the crack, the stiffness matrix of the beam element is modified. The beam element with modified stiffness matrix is then fit into the complete finite element assemblage representing a cracked rotor system. In this study the natural frequencies of cracked and un-cracked rotor are found using Ansys and then the variations in natural frequencies of the rotor with varying depths at a given location are estimated. This analysis is done for two different geometries of shaft and results are compared. Experimental investigations were carried out and frequencies of cracked and un-cracked rotor are determined and the results are compared.