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© Fraunhofer Improved fatigue design methods for offshore wind turbine rotor blades considering non-linear Goodman analysis combined with finite element.

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Presentation on theme: "© Fraunhofer Improved fatigue design methods for offshore wind turbine rotor blades considering non-linear Goodman analysis combined with finite element."— Presentation transcript:

1 © Fraunhofer Improved fatigue design methods for offshore wind turbine rotor blades considering non-linear Goodman analysis combined with finite element analysis Stefan Wessels Michael Strobel Dr. Arno van Wingerde Isabel Koprek Dr. Hans-Gerd Busmann

2 © Fraunhofer Outline Idea & Motivation Used Fundamentals Structural Model Programming the fatigue Analysis based on NLGD´s Validation Fatigue Analysis on a rotor blade model Conclusion & Outlook

3 © Fraunhofer Idea & Motivation Square – Cube – Law leads to increasing blade weights Conservative approaches in blade design Material properties of fiber composites can be exploited further Goal: Weight & Cost reduction in the early design stage Track: Damage calculation using FEM and Non-Linear-Goodman-Analysis

4 © Fraunhofer Used Fundamentals Non-Linear-Goodman-Diagram (NLGD) Rain-Flow-Counting Miner-Sum

5 © Fraunhofer Structural Model FEM-Rotor-Blade-Model Model generated with FOCUS ANSYS-Solver 8-noded SHELL99-Elements 4-noded SHELL181-Elements Loads applied on arbitrary cross section CARDS (JAVA - Open-Source Postprocessor)

6 © Fraunhofer Principal procedure Programming the fatigue Analysis based on NLGD´s

7 © Fraunhofer Programming the fatigue Analysis based on NLGD´s Programming the NLGD Transforming S-N-curve data Determination of maximum number of cycles out of NLGD Using method to find a point in a triangle Logarithmic interpolation φ

8 © Fraunhofer Validation Results are compared with FOCUS FOCUS beam model Improved method 3D FEM-Model Four points on an arbitrary cross section are investigated Comparison of damage for UD-Laminate and +/- 45°-Laminate Three different approaches

9 © Fraunhofer Validation Comparison of the results Big deviations Comparison of strain-time-series Factor k to adjust the damage calculation

10 © Fraunhofer Fatigue Analysis on a rotor blade model Transition zone of webs of particular interest Analysis of: UD-Laminate in spar caps +/-45°-Laminate for outer shell Adhesive bonding

11 © Fraunhofer Fatigue Analysis on a rotor blade model Results of the damage calculation Damage of UD-Lamiante in the spar caps Increasing damage towards the tip due to: Deceasing thickness and cross section area Constant load on the blade section Change from two to one web Damage of +/-45°-Lamiante Damage of adhesive bonding

12 © Fraunhofer Conclusion & Outlook The Improved fatigue design method helps: Enhancing the material usage Detecting critical areas in terms of fatigue Increases the accuracy of the material prediction (using NLGD´s) Issues to improve Check other approaches for damage accumulation The way of applying loads on 3D-FEM-Models

13 © Fraunhofer Thank you for your attention! Dziękuję bardzo!


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