Shrink-fitted joint behavior using three-dimensional solid finite elements in rotor dynamics with inclusion of stress-stiffening effect

Eerik Sikanen,Janne E Heikkinen,Jussi Sopanen

doi:10.1177/1687814018780054

Eerik Sikanen, Janne E Heikkinen + Show 1 more

Open Access

https://doi.org/10.1177/1687814018780054

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Abstract

In this article, the contact behavior of a shrink-fitted joint in a rotor assembly at different spin speeds is studied, using the three-dimensional solid finite element approach. A custom frictionless contact model is proposed and extensively tested by means of simulation. The theory for solving pre-stressed damped eigenvalue problem is presented and implemented, and the results are presented in Campbell diagram form. Two sample rotor assemblies are studied. In addition, experimental modal analysis results of a shrink-fitted joint with various interferences are presented and numerically studied. The reduction of the interference of the shrink-fitted joint due to centrifugal forces at high-speed operation as well as the contact status are updated at each rotational speed step. The inclusion of stress-stiffening effect is studied in detail. The comparison of the Campbell diagram results with the results obtained using a commercial finite element software (Ansys) shows a good agreement.

Highlights

In high-speed machinery applications, rotor dynamic analysis is important part of the design progress
Often used one-dimensional (1D) beam element approach in rotor dynamics can represent only flexible shafts while the disks and impellers are modeled as rigid mass points.[1]
Certain material properties of individual components are verified by measuring mass properties and the lowest free–free natural bending mode (BM) frequencies

Summary

Introduction

In high-speed machinery applications, rotor dynamic analysis is important part of the design progress. Effects of deformable shaft cross section and flexible disks, and turbine blades are required These features enable the inclusion of the stress-stiffening effect when the total stiffness of the rotor assembly is affected by the internal stress of the component.[2] These aforementioned effects can be included when using twodimensional (2D) axisymmetric harmonic or threedimensional (3D) solid finite elements (FE).[3,4,5] The use of a 2D element is usually limited to axisymmetric structures and axisymmetric loads, whereas 3D elements can be used to describe, in practice, any rotating structure. Chen et al.[11] performed pre-stressed modal study of a hollow shaft assembly with shrink fits using Ansys They used the native TARGE170 and CONTA174 contact elements of the software, and in order to verify the numerical results, experimental modal analysis (EMA) was performed. The strain matrix is formed using the partial derivatives of the shape functions as follows

À D1 D1 0 0

Experimental results from the test shaft assembly

Conclusion