Advanced Wind Turbine Program Next Generation Turbine ... - NREL

A blade certification testing program was conducted at the National Wind Technology Center
(NWTC) in Golden, Colorado, under the supervision of personnel of the National Renewable
Energy Laboratory. Fatigue testing of a GE34a blade began in August 2001, and was completed
January 10, 2002. The same blade was used as had been subjected to the static testing described
above. The objective of the fatigue test was originally to conduct a limited life fatigue test in order
to give basic assurance that no major catastrophic fatigue failures are likely. The target number
of test cycles was 300,000 for a ten percent life. This was based on observations that past
fatigue testing has revealed problems early in the test duration. Later, this objective was expanded
to include a full 20-year life of damage using a one-million-cycle load duration. The test
operated for 1.9 million cycles.
(a) Blade Setup
(b) Two-Axis Hydraulic Actuator
Figure 29. NWTC Fatigue Test Setup
Loads were provided to NWTC by GE Wind to represent a 3-million-cycle design life. The testing
began with the 3 million cycle loads. Beginning at approximately 928,000 cycles, however,
the test loads were increased to accelerate the test to achieve 100% damage in 1 million cycles.
Table 5 summarizes the operationally equivalent fatigue damage resulting from the fatigue test at
various spanwise locations on the blade. These results were determined via finite element analysis
of the blade. These results indicate that the critical test regions of the blade were tested to at
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