Structural Change Identification at a Wind Turbine Blade using Model Updating

K. Schröder, S. Grove, S. Tsiapoki, C.G. Gebhardt and R. Rolfes

EERA DeepWind’18, 18.01.18

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Content

I. Motivation

II. Optimization based model updating

III. Rotor blade test

IV. Model updating at the rotor blade1. Damage localization2. Ice accretion

V. Conclusion and Outlook

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Motivation

• Remote location

• Rotor blades: costly and time-consuming repair

• Ice accretion: - Risk of ice throw

- Undesired loads

Localization and quantification of structuralchanges using model updating

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Finite Element Model Updating

Damage event

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Deviation between numerical model andmeasured data

Modal parameters

Transmissibility functions

• Eigenvalues• Mode shapes

Quantification of the „difference“ between model and measurement

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Minimization of the deviation

• Nonlinear• Constrained• Nonconvex• Several local minima

Global optimization algorithm:Simulated Quenching

Local optimization algorithm:Sequential Quadratic Programming

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Rotor blade test

• Hammer excitation

• 12 measurement channels

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• Hammer excitation

• 12 measurement channels

• Ice mass

• Damage

Trailing edge bondline: Spot of damage initiation

Trailing edge – PressureSide (outside)

Rotor blade test

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Numerical Modeling

•Rectangular Cross Section

•Known: EI and mass

•26 Timoshenko beam elements

•Clamping at blade root

•Material damping

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Numerical validation

Stiffness reduction

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Numerical validation–Modal Parameters

Parameter number

Parameter number

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Numerical validation –Transmissibility Functions

Parameter number

Parameter number

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Ice accretion

• 4 steps

• Variation of density

• Optimization problem:

• Step 3: 14,4kg at 32m-33m and 33m-34m

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Ice localization – Modal Parameters

• Correct Localizations in runs 1, 3, 7, 9 und 11

• Verification using objective function value

• Ice localization using modal parameters is possible

Parameter number

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Ice quantification – Modal ParametersSt

iffne

ssPa

ram

eter

4 in

%

Ice set (rotor blade mass in %)0.1 0.3 0.6 0.9

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Conclusion & Outlook

• Updating in numerical examplesand for ice quantification successful

• Minimization using global two-step optimization algorithm• No success for damage localization using measured data• Modal parameters superior to transmissibility functions

• Investigate more advanced metrics for model updating• Application to changing conditions (in situ)

Conclusion

Outlook

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Thank you for your attention!

Leibniz Universität HannoverInstitute of Structural Analysis (ISD)Appelstraße 9a, 30167 Hannover

+49 511 762 8063k.schroeder@isd.uni-hannover.de