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Strength and fatigue testing of rotors of large size wind turbines

Objective

The objective of this project is to establish a rationale of strength and fatigue testing.


If wind energy is to contribute to a greater extent to the electricity production, the generating cost has further to be reduced. This can be achieved by the reduction of machine manufacturing cost and by the improvement of system and structural reliability. Machines may become improved by thorough fatigue life analysis in the design phase. An important cost driver of a wind turbine is among others the rotor. A sensible method of making turbine rotors cheaper is obtained by making them lighter. To guarantee a rotor blade against early failure, whether caused by insufficient strength or fatigue, it is necessary to check the design by an approval test. In particular the fatigue life analysis is still quite unreliable, a specimen tested in laboratory conditions will fail quite often by Miner summations between 0.25 and 4 for constant amplitude test and between 0.6 and 1.6 for variable amplitude test. One method, and maybe the only method, to proof the reliability of the design is to perform a full scale strength and fatigue test. These tests might also be required in future by the certification authorities to get a full type certificate.

Main project items :
- Recommendations on procedures and criteria with regard to :
. strength tests (ST);
. dynamic tests (DT);
. fatigue tests (FT).
[Address the "should" and if so "when" question]
- Ibid on test procedures, such as :
. number of cross sections at which design loads has to be simulated (ST & FT);
. elastic behaviour, natural frequencies and ditto modes and mechanical damping (DT);
. rational on strength and fatigue boundary (ST & FT);
. rational on the translation of design to that fatigue spectrum (FT); . indication of strength and fatigue margins.
[Address the "how" question]
- Demonstration of these kind of tests.
- Cost & benefit analyses.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

ENERGY RESEARCH CENTRE OF THE NETHERLANDS
Address
Westerduinweg 3
Petten
Netherlands

Participants (5)

CENTRO DE INVESTIGACIONES ENERGETICAS, MEDIAMBIENTALES Y TECNOLOGICAS
Spain
Address
22,Avenida Complutense 22
28040 Madrid
GERMANISCHER LLOYD AG
Germany
Address
Vorsetzen 32
Hamburg
Risø National Laboratory
Denmark
Address
399,Frederiksborgvej 399
4000 Roskilde
STORK PRODUCT ENGINEERING BV
Netherlands
Address
229,Czaar Peterstraat 229
1000 AJ Amsterdam
T.G. Teknikgruppen AB
Sweden
Address
5,Allfarvägen 5
191 91 Sollentuna