Prof. Dr.-Ing. Theo Kiesel

Industrial PhD

The Finite Element Method in Rotordynamics

Rotordynamics is a comparably young branch in the field of Applied Mechanics, in which even today fundamental knowledge is still being built up. Like in almost any area of engineering science, the practicability on real world machines or constructions depends on the availability of suitable computational methods. The rise of the Finite Element Method led to a stimulation also in rotordynamics. Critical voices point out, however, that rotordynamics is lagging behind the development in general dynamics. For problems in the field of structural dynamics , the use of 3D solid finite elements has become indispensable, whereas in rotordynamics almost exclusively beam elements are applied. At a first glance it appears to be natural to intellectually divide a rotating shaft into sections which can be represented by axialsymmetric beam elements. The process is intuitive and results in a model that can be solved with reasonable numerical effort. However, when dealing with complex rotor geometries, this approach will soon reach its limits. This is due to the fact that a beam-element model needs to be created manually, and can not be derived automatically from the CAD-model, as in the usual case. Moreover, beam-element models have problems dealing with axially asymmetric rotors, and mathematically they fail completely if the rotor as well as the stator shows nonlinear behavior. As an alternative, it might be useful to use 3D solid finite elements, which in that case need to fulfill specific requirements regarding the element formulations. This alternative shall be examined within a dissertation project, using a complex rotor system out of the industry as an application example.