Simulation of mode-locking phenomena in a complex nonlinear rotor system using 3D solid finite elements

The most common simulation approach in rotor dynamics is based on beam models. Usually, these models are very compact and come at low computational costs. However, they are afflicted with a number of limitations, making them insufficient for the analysis of more complex rotor systems, which require 3D solid modeling. General purpose FEM codes offer full 3D solid modeling capabilities, but the question still remains, whether they are capable of correctly taking into account all the effects that arise from rotation. This paper provides an example of a complex, highly nonlinear rotor system, which cannot be simulated or even modeled accurately by using beam elements, but rather requires 3D solid modeling. ABAQUS is used-as a representative example for a general purpose FEM code-to build up an appropriate model. By doing so, the paper addresses the question, whether a general purpose FEM code is able to cover the necessary rotor dynamic effects. The model which is derived here takes into account nonlinear stiffness behavior, and includes contact between different components of a rotor assembly. The objective is to simulate a run-up through a bending resonance, using direct time integration. The simulation results are compared with experiments, showing good consistency. During the crossing of the critical speed due to the bending resonance, mode-locking can be observed in the experiment and is well represented by the simulation model.