The National Wind Technology Center at the National Renewable Energy Laboratory and Sandia National Laboratories collaborate on the testing of full-size wind turbine blades. One of the tests performed on a wind turbine blade is a static-pull test. A distributed and controlled static load is applied to the blade using a four-point Whiffle-tree arrangement, as shown in this photo. The blade-to-hub attachment, or root end of the wind turbine blade, is held constant by a large seismic mass and restraining structure. Starting at a zero net load, the load on the blade is incremented in steps, holding at each step for a short period of time. This “step-load increase and hold” sequence is repeated until the wind turbine blade breaks.

One of the several diagnostic techniques used during a static test is acoustic emission (AE) nondestructive testing (NDT). Before the test, an array of AE...

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