Experimental Results of Structural Health Monitoring of Wind Turbine Blades

Abstract

A 9 meter TX-100 wind turbine blade, developed under a Sandia National Laboratories R&D program, was recently fatigue tested to blade failure at the National Renewable Energy Laboratories, National Wind Technology Center. The fatigue test provided an opportunity to exercise a number of structural health monitoring (SHM) techniques and nondestructive testing (NDT) systems. The SHM systems were provided by teams from NASA Kennedy Space Center, Purdue University and Virginia Tech (VT). The NASA and VT impedance-based SHM systems used separate but similar arrays of Smart Material macro-fiber composite actuators and sensors. Their actuator activation techniques were different. The Purdue SHM setup consisted of several arrays of PCB accelerometers and exercised a variety of passive and active SHM techniques, including virtual and restoring force methods. A commercial off-the-shelf Physical Acoustics Corporation acoustic emission (AE) NDT system gathered blade AE data throughout the test. At a fatigue cycle rate around 1.2 Hertz, and after more than 4,000,000 fatigue cycles, the blade was diagnostically and visibly failing at the blade spar cap termination point at 4.5 meters. For safety reasons, the test was stopped just before the blade completely failed. This paper provides an overview of the SHM and NDT system setups, and some test results.

Review on Structural Health Evaluation with Acoustic Emission

“…As in the Sandia report [11], Weihnacht et al [107] discussed testing of large FRP components. In one of their tests, they needed to place 64 sensors over a 38-m long blade at 3 to 5 m sensor spacing.…”

“…Two recent review articles [9,10] on bridge and pressure-vessel inspection are noteworthy in connection to the topic of this introduction. Another review was published as a Sandia report, comparing AE with other methods for structural health monitoring (SHM) in evaluating damages to a full-scale wind turbine blade, and demonstrating the advantages of AE over others [11]. The present author also prepared survey papers on structural diagnosis [12] and on composites [13].…”

Acoustic emission non-destructive testing of structures using source location techniques.

“…The first example of an acoustic emission test setup and analysis is the fatigue test of the Sandia TX-100 blade [14,15] performed at the National Wind Technology Center (NWTC). This was a 9-meter wind turbine blade with a special skin designed to rotate the tip angle of incidence as the load on the blade increased.…”

“…colors -salmon,blue,green,cyan,red, ! black n=0 do 10 i=1,24 do 9 j=1,9 if(i.eq.nsn(j))go to 10 9 continue n=n+1 snx(n)=senx(i) sny(n)=seny(i) 10 continue call plinit() call plcol0 (15) call plschr(0.,1.0) call plenv(650.,950.,-50.,250.,1,1) call pllab('X -mm','Y -mm','compression side') call plcol0(mclr(1)) call plpoin(nn1,x1,y1,42) …”

A Multi-scale Approach to Statistical and Model-based Structural Health Monitoring with Application to Embedded Sensing for Wind Energy

“…A variety of data acquisition and analysis methods have been applied to the problem of fatiguing wind turbine rotor blades, and the CX-100 rotor blade has been a specimen of particular popularity [7,15,20,[102][103][104][105][106][107][108]. The experiment considered in this example was the CX-100 rotor blade fatigue test described in Section 2.5.…”