The dynamics of bolted and laminated rotors

A significant proportion of all of the rotating machines in operation have rotors which are either bolted or laminated construction. Gas-turbines and small steam turbines frequently comprise a set of discs clamped together by either a single central bolt or a small number of bolts on a small pitch circle diameter thereby trapping the roots of the turbine blades between adjacent discs. Most electrical machines (except permanent magnet machine) have a solid forged or fabricated shaft onto which a stack of laminations is fitted. The dynamics of such rotors are potentially quite different from the dynamics of a solid rotor of similar dimensions. This paper reports early progress on an investigation into the behaviour of such rotors. A test-rig is described together wish some experimental results from this rig. Comparisons are made between these test results and predictions from simulations.