Analysis of coupling mechanism in lateral/torsional rotor vibrations

Coupling phenomena of lateral-torsional vibrations in rotating machinery can lead to rotor unstable behaviour. In some types of rotating machinery, the angular speed is subjected to wide ranges of change. The problem is to find the range of angular speeds for which a machine exhibits stable behaviour in the presence of the coupling of dynamical modes. Usually, unstable regions are in the vicinity of angular speeds where maps of natural frequencies for both dynamical systems intersect with each other. Using the root locus method, it is described which intersections lead to unstable vibrations and why.