Dynamics and Control of a Rotor Using an Integrated SMA/Composite Active Bearing Actuator

It has been shown that judicious integration of SMA wires or stri ps within composite components of certain geometries can lead to substantially enhanced dynamic effects within the component. These effects relate to natural frequency placements, m ode shapes, and forced response characteristics, in particular. One application area of conside rable interest involves the installation of bespoke technology exploiting this controllability within rotor syst ems, and this is the subject of this paper. It is shown that for a laboratory rotor system suppo rted n two bearings, one of which is an active component comprising a cylindrical sleeve with speciall y configured and integrated SMA strips, the critical speeds can be usefully shifted about their nomi nal values. The paper shows how such an active bearing installation can be designed and discusses the many trade-offs required to optimise the performance in a useful way. It is shown that the princ i al compromises relate to stress in the composite host, physical size and shape of this component, quantit y and distribution of SMA, and the local operating dynamics. It is also shown that glassepoxy is superior to graphite-epoxy in terms of dynamic controllability for the composite cylindrical s leeve host component when used as an active support for one of the bearings, and that this useful perf ormance can be accentuated by means of careful design.