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Stefan Wessels Michael Strobel Dr. Arno van Wingerde Isabel Koprek Dr. Hans-Gerd Busmann

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. Outline. Idea & Motivation Used Fundamentals

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Stefan Wessels Michael Strobel Dr. Arno van Wingerde Isabel Koprek Dr. Hans-Gerd Busmann

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  1. 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. 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. 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 http://www.enercon.de

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

  5. 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. Programming the fatigue Analysis based on NLGD´s • Principal procedure

  7. 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. 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. Validation • Comparison of the results • Big deviations Comparison of strain-time-series  Factor k to adjust the damage calculation

  10. 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. Fatigue Analysis on a rotor blade model • Results of the damage calculation • 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 adhesive bonding Damage of +/-45°-Lamiante Damage of UD-Lamiante in the spar caps

  12. 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. Thank you for your attention! • Dziękuję bardzo!

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