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Title:
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Strength and fatigue testing of large size wind turbine rotors: vol. 1:rationale and directions
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Author(s):
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Published by:
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Publication date:
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ECN
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1996
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ECN report number:
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Document type:
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ECN-C--95-052
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ECN publication
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Number of pages:
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Full text:
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207
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Download PDF
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Abstract:
Some 20 industries were approached through a questionnaire. The workconcerned full size Natural Vibration Tests (NVT), Static Strength Tests
(SST) and Fatigue Strength Tests (FST). Principal objectives were to
determine points of departure to arrive at well defined mechanical test
results in relation to design and manufacturing, to give recommendations on
procedures and methodologies how to perform these tests, and to address the
costs and benefits. Mechanical tests were to be executed also. The work is
documented in three different volumes: this one, vol. 2: Full-size NVT and
SST. A reference case, and vol. 3: Full-size FST. A reference case. The tests
concern modelling, calculations, production methods or materials. With regard
to the NVTs the principal objectives have been formulated, implying a
specification which key quantities should be verified (mass, location of
center of gravity, stiffness and resonance frequencies). The SST has been
elaborated in terms of the performance of the Limit Load Test(s) (LLT), the
Ultimate Load Test(s) (ULT) and a Failure Load Test (FLT), particularly in
relation to the test objectives. A guideline on the practical performance of
the SSTs was drafted, containing directions on different items. The FST has
been elaborated in terms of the performance of an Ultimate Fatigue Strength
Test(s) (UFT) and subsequently the Residual (Ultimate) Strength Test(s) (RST)
and a Residual Failure Strength Test (RFST), all in relation to the test
objectives. Also a guideline on the practical performance of the FSTs was
drafted, containing directions on different items. Present regulations
(standards) of CIWI, DS, GL and IEC can certainly be improved. The
recommended safety factors being it on loads, or on materials or even on the
product of them show too large differences. More attention should be paid to
a consistent design approach of static versus fatigue strength and to the
possibility that safety factors can be verified through proper laboratory
tests. The very first blade the manufacturer will rely on, shall be used as
the first test specimen for the performance of the NVTs and the SSTs. 22
figs., 15 tabs., 20 refs.
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