A Rayleigh-Type Inclusion of Shaft Inertia in Torsional Vibration Analysis

This paper considers the problem of properly accounting for the shafting inertia in torsional vibration analysis. It begins with a brief review of the two well-established methods: (1) arbitrarily lumping the shaft inertia with that of the disks, and (2) the continuum model, which considers both the flexibility and the inertia as distributed properties. Comments regarding the advantages and disadvantages of each are offered as motivation for the new method to be presented here. The new approach is then developed, using a Rayleigh-type approximation for the displacement between stations, with the full theory underlying it. The results of all three methods are then compared by application to several test cases.