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

Theo Kiesel,Steffen Marburg

doi:10.1177/0954406215617196

Abstract

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.

Highlights

The finite element method (FEM) has become a powerful tool for researchers and engineers to perform rotor dynamic analysis
An example of a complex and highly nonlinear rotor system has been presented in this paper
The system cannot be simulated or even modeled accurately by using beam elements, but rather requires 3D solid modeling. This is due to the complexity and the highly nonlinear system behavior, especially with regard to the contact situation between the two-piece coupling and the rotor

Summary

Introduction

The finite element method (FEM) has become a powerful tool for researchers and engineers to perform rotor dynamic analysis. General purpose FE codes offer full 3D solid modeling capabilities to analyze structural dynamic problems, the most common approach in rotor dynamics consists of using beam-element models,[1,2] by some authors referred to as shaft-line models.[3] The name arises from the process of creating the mesh by placing nodes along the shaft line. These models are very compact, consisting mainly of beam elements and concentrated masses equipped with moments of inertia to account for the gyroscopic effects.

Design of RotaƟng Machinery

Summary and conclusions