Rotating Systems
The available static and dynamic analysis capabilities can be used to analyze rotating systems, which imply additional constraints to the solution.
Statics
In a quasi-static analysis, which may include contact at the hub, the centrifugal forces due to rotation are taken into account. The reference system is co-rotating. The static analysis is possible below critical speed.
In a linear analysis, the centrifugal stiffness and the geometric stiffness at the given rotational speed are taken into account. In a geometrically nonlinear analysis, an update of the centrifugal forces will take place.
Dynamics
In order to get the relation between eigenfrequencies and rotational speed an automatic procedure is available which directly generates all values for a Campbell diagram.
For dynamics of rotating systems, the assumption is a linearized equation of motion with constant coefficients. Usually, a co-rotating reference system is taken. If rotating and non-rotating parts are present, the rotating part is taken as rigid and the reference system is the inertial system.
In the case of a coupling of rotating and non-rotating parts, no restrictions have to be observed for the non-rotating parts, but the rotating parts have to be taken as rigid and at a constant rotational speed. In addition, the rotating parts have to be symmetric.
For such configuration, all direct and modal methods in time and frequency domain can be applied. During response analysis the gyroscopic matrix is taken into account. In addition, a steady-state response is possible, where for a periodic excitation several frequency response analysis results are superposed.
In the case of dynamics in a co-rotating reference system, no additional restrictions have to be observed for the non-rotating parts, but the support has to be symmetric and the rotational speed of the reference system has to be constant.
Also for such configuration, all direct and modal methods in time and frequency domain can be applied taking into account the gyroscopic matrix. In addition, a steady-state response is possible, where for a periodic excitation several frequency response analysis results are superposed.
For dynamics in the co-rotating reference system, modal steady-state response is of particular importance. First, the static stresses under centrifugal load are determined. Then, with geometrical and centrifugal stiffness, the static displacements are derived. On the basis of real eigenvalue analysis, several modal frequency response analyses are performed for each harmonic. After back transformation to physical space, the results for all harmonics and the static case are superposed in the time domain.
