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Thursday, 13 March 2014
09:00 - 10:30 Materials: Challenges and potentials
Hardware Technology  


Room: Ponent
Session description

Time is money: how can advanced materials with high potential for driving down costs be utilised in wind energy turbines within short timeframes? What can we learn from material and component testing of products currently under certification to shorten the time-to-market of the next-generation products? Does the strong worldwide competition between turbine manufacturers accelerate the use of new materials? These questions will be discussed with a view on the introduction of a new adhesive for blade bonding, testing of rotor blades, high-strength iron for rotor shafts, and superconducting materials for new generators.

Learning objectives

  • Discover ideas on how new materials support the development of new turbine components
  • Understand the interdependence between materials development, testing and product development
  • Recognise the role of testing to decrease the time-to-market of new components
Lead Session Chair:
Hans-Gerd Busmann, Fraunhofer Institut für Windenergie und Energiesystemtechnik IWES, Germany
Thes Rauert University of Applied Sciences Hamburg, Germany
Co-authors:
Thes Rauert (1) F P Peter Dalhoff (1) Hans Kyling (2) Karina Holz (3) Jörg Winkelmann (3)
(1) University of Applied Sciences, Hamburg, Germany (2) Fraunhofer IWES, Bremerhaven, Germany (3) Suzlon Energy GmbH, Rostock, Germany

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2014 and are published here unedited

Mr. Rauert holds a master’s degree in mechanical engineering and is currently working as a research assistant at the University of Applied Sciences in Hamburg. His research focus lies on the fatigue behavior and wear mechanisms of the rotor shaft. His work is part of a joint research project together with Fraunhofer IWES and Suzlon.

Abstract

Fatigue life of rotor shafts in theory, practice and in a full scale testing environment

Introduction

The rotor shaft of a wind turbine is subjected to great loads during turbine operation.
A lack of testing experience is being compensated by safety factors. This leads to high weights of 20t and above for the rotor shaft of multi megawatt turbines.
The objective of this research article is to show how the fatigue life of a rotor shaft is commonly assessed, how wear patterns can still emerge and how a full scale accelerated fatigue test will look like.


Approach

A systematic literature review of fatigue life assessment for components made from forged steel was done.
In addition the loads on the rotor shaft and different wear mechanisms were analyzed.
For the definition of a test strategy a research on testing concepts in the wind industry and other industries was done.


Main body of abstract

On the one hand rotor shafts of wind turbines seem to be greater and heavier than they need to be, due to a lack of experienced data from full scale fatigue testing and a compensation through safety factors. On the other hand wear mechanisms at the contact region between the rotor shaft and the shrink fitted inner ring of the main bearing can be observed. These wear mechanisms are also known from other industries. Shear stresses in the contact region that result from the rotating bending moment at the rotor shaft eventually overcome the frictional connection and lead to a relative motion between rotor shaft and inner ring. These relative motions can cause surface deterioration and thus a degradation of the fatigue strength of the component. The component’s life span, estimated by common life time assessment methods, will decrease unnoticed.
To investigate both the fatigue behavior of the whole component and wear mechanisms a full scale fatigue test has to be carried out.



Conclusion

The goals of the investigations and the results from the literature review on fatigue life time assessment and wear mechanisms are setting boundaries for a full scale fatigue test of the rotor shaft. Within these boundaries different alternatives for a test strategy are being developed and evaluated via a morphological analyses. The final strategy is serving as a specification for the development of a full scale test bench.




Learning objectives
The article will provide information on the common method of fatigue life assessment as well as wear mechanisms in a shrink fitted contact under rotational bending. It also shows the path to a full scale fatigue test of the rotor shaft.