Torsional vibrations occur due torelative oscillatory motions superposed on the mean rotation. Rotating systems at running speed near the natural frequencies are prone to excessive angular deflections and hence large stresses which can cause rotating components failure or premature fatigue failures. The objective of the present work is to study the torsional vibration characteristics of multi-rotor and gear-branched systems suing finite element method. Finite element method (FEM) is a numerical technique based on principle of discretization to find approximate solutions to engineering problems. The information about the natural frequencies for rotating systems can help to avoid system failure by giving the safe operating speed range. In the present work, finite element method has been used to find these natural frequencies for different possible cases of multi-rotor and gear-branched systems. The various mode shapes for several cases are also shown to illustrate the state of the system at natural frequencies. The results obtained have been compared with Holzer’s method and transfer matrix method to establish the effectiveness of finite element method for such systems.
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