Abstract
In this paper a general transfer matrix method (TMM) for rotors containing global and local coupler offset was derived. Rotor response due to imbalances and offsets are then studied via the developed method. The studies showed both global and local offsets played as an external excitation that is a combined effect of all the elements behind the offset. Differences between global offset and local offset were compared and the results showed both types basically retain the same mode patterns but different jumps at the offset. The global offset, yet, imposed more significant dynamic effects since all the offsets accumulate thereafter. The whirling orbits in front and behind the offset were illustrated as well. The results, as expected, showed global offset appeared much larger radii especially after offset. The rotor's whirling orientation reversed, as rotation fell within a certain range and this feature was not changed by offsets. The TMM proposed by this study can be well applied to multiple global and local offsets.
Highlights
Rotors have been extensively used in mechanical engineering
Approaches to dynamic analysis of rotor systems can be divided into two main branches
Saavedra and Ramirz [20] proposed a theoretical model of a rotor-bearing system using a new coupling finite element stiffness matrix and discussed the vibration behaviour due to shaft misalignment and residual unbalance
Summary
Rotors have been extensively used in mechanical engineering. The dynamic behaviour of rotors has gained interests for over a century. Xu and Marangoni used a universal joint to model misalignment and utilized the component mode synthesis to analytically [14] study and experimentally [15] validate their calculations In their model, the misalignment effect was represented by an additional bending moment of even multiples of rotational speed. Saavedra and Ramirz [20] proposed a theoretical model of a rotor-bearing system using a new coupling finite element stiffness matrix and discussed the vibration behaviour due to shaft misalignment and residual unbalance. Their results showed the vibration induced by shaft misalignment was due to the variation in coupling stiffness and the generated forcing frequencies were harmonics of the rotational speed. Numerical examples of local and global offset for a typical rotor system are studied and compared with
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