Title:

Method to predict fatigue lifetimes of GRP wind turbine blades andcomparison with experiments


Author(s):



Published by:

Publication date:

ECN
Energy Efficiency in Industry

1996


ECN report number:

Document type:

ECNRX96036

Other


Number of pages:

Full text:

2

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Abstract:
A method to predict fatigue lifetimes of fiber reinforced plastics inwind turbine blades is described. Measured fatigue properties of a material
are taken into account so that credit can be given to materials with improved
fatigue properties. The large number of test results should also give
confidence in the fatigue calculation method for fiber reinforced plastics.
The method uses the PalmgrenMiner sum to predict lifetimes and is verified
by tests using well defined load sequences. Even though this approach is
generally well known in fatigue analysis, many details in the interpretation
and extrapolation of the measurements need to be clearly defined, since they
can influence the results considerably. The following subjects will be
described: method to measure SN curves and to obtain tolerance bounds,
development of a constant lifetime diagram, evaluation of the load sequence,
use of PalmgrenMiner sum, and requirements for load sequence testing. The
fatigue lifetime calculation method has been compared with measured data for
simple loading sequences and the more complex WISPERX loading sequence for
blade roots. The comparison is based on predicted mean lifetimes, using the
same materials to obtain the basic SN curves and to measure laminates under
complicated loading sequences. 7 figs., 5 tabs., 24 refs.
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