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Research Papers: Gas Turbines: Structures and Dynamics

Modeling and Validation of the Nonlinear Dynamic Behavior of Bolted Flange Joints

[+] Author and Article Information
C. W. Schwingshackl

Imperial College London,
London, UK
e-mail: c.schwingshackl@ic.ac.uk

D. Di Maio

University of Bristol,
Bristol, UK
e-mail: Dario.DiMaio@bristol.ac.uk

I. Sever

e-mail: Ibrahim.Sever@Rolls-Royce.com

J. S. Green

e-mail: Jeff.Green@Rolls-Royce.com
Rolls-Royce,
Derby, UK

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 28, 2013; final manuscript received July 3, 2013; published online September 20, 2013. Editor: David Wisler.

J. Eng. Gas Turbines Power 135(12), 122504 (Sep 20, 2013) (8 pages) Paper No: GTP-13-1200; doi: 10.1115/1.4025076 History: Received June 28, 2013; Revised July 03, 2013

Linear dynamic finite element analysis can be considered very reliable today for the design of aircraft engine components. Unfortunately, when these individual components are built into assemblies, the level of confidence in the results is reduced since the joints in the real structure introduce nonlinearity that cannot be reproduced with a linear model. Certain types of nonlinear joints in an aircraft engine, such as underplatform dampers and blade roots, have been investigated in great detail in the past, and their design and impact on the dynamic response of the engine is now well understood. With this increased confidence in the nonlinear analysis, the focus of research now moves towards other joint types of the engine that must be included in an analysis to allow an accurate prediction of the engine behavior. One such joint is the bolted flange, which is present in many forms on an aircraft engine. Its main use is the connection of different casing components to provide the structural support and gas tightness to the engine. This flange type is known to have a strong influence on the dynamics of the engine carcase. A detailed understanding of the nonlinear mechanisms at the contact is required to generate reliable models and this has been achieved through a combination of an existing nonlinear analysis capability and an experimental technique to accurately measure the nonlinear damping behavior of the flange. Initial results showed that the model could reproduce the correct characteristics of flange behavior, but the quantitative comparison was poor. From further experimental and analytical investigations it was identified that the quality of the flange model is critically dependent on two aspects: the steady stress/load distribution across the joint and the number and distribution of nonlinear elements. An improved modeling approach was developed that led to a good correlation with the experimental results and a good understanding of the underlying nonlinear mechanisms at the flange interface.

Copyright © 2013 by Rolls-Royce plc
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References

Figures

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Fig. 1

The linear flange FE model, (a) assembled model, (b) the bolt, and (c) details of the linear interface mesh

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Fig. 2

The manufactured test piece

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Fig. 3

Static normal load distribution at the (a) bolt-flange and (b) flange-flange contact interface from ABAQUS

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Fig. 4

Nonlinear mesh with (a) fixed bolt and (b) nonlinear bolt contact. Each dot is an element, and the color represents the applied static normal load.

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Fig. 5

Additional nonlinear mesh configurations for the flange

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Fig. 7

Second torsion mode with flange position

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Fig. 8

Measured damping behavior for second torsion mode

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Fig. 9

Excitation and response location of nonlinear model

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Fig. 10

Frequency response of 153 element mesh at different amplitudes

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Fig. 11

Nonlinear damping behavior

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Fig. 12

Damping behavior with and without bolt head contacts

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Fig. 13

Damping behavior with and without bolt head contacts

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Fig. 14

Energy dissipation at the contact interface for 153 and 367 elements at 1 g acceleration

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Fig. 15

Correlation of original (before updating) model with measurement data

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Fig. 16

The (a) convex flange geometry and (b) the modified elements

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Fig. 17

Damping behavior for different updated static normal loads

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Fig. 18

Correlation of original model with measurement data

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