Increasing demand and deployment of wind power has led to a significant increase in the number of wind-turbine blades
manufactured globally. As the physical size and number of turbines deployed grows, the probability of manufacturing
defects being present in composite turbine blade fleets also increases. As both capital blade costs, and operational and
maintenance costs, increase for larger turbine systems the need for large-scale inspection and monitoring of the state of
structural health of turbine blades during manufacturing and operation critically increase. One method for locating and
quantifying manufacturing defects, while also allowing for the in-situ measurement of the structural health of blades, is
through the observation of the full-field state of deformation and strain of the blade. Static tests were performed on a
nine-meter CX-100 composite turbine blade to extract full-field displacement and strain measurements using threedimensional
digital image correlation (3D DIC). Measurements were taken at several angles near the blade root,
including along the high-pressure surface, low-pressure surface, and along the trailing edge of the blade. The overall
results indicate that the measurement approach can clearly identify failure locations and discontinuities in the blade
curvature under load. Post-processing of the data using a stitching technique enables the shape and curvature of the
entire blade to be observed for a large-scale wind turbine blade for the first time. The experiment demonstrates the
feasibility of the approach and reveals that the technique readily can be scaled up to accommodate utility-scale blades.
As long as a trackable pattern is applied to the surface of the blade, measurements can be made in-situ when a blade is
on a manufacturing floor, installed in a test fixture, or installed on a rotating turbine. The results demonstrate the great
potential of the optical measurement technique and its capability for use in the wind industry for large-area inspection.
KEYWORDS: Digital image correlation, Structural health monitoring, 3D image processing, Cameras, Sensors, Calibration, Photogrammetry, Fiber optics sensors, 3D acquisition, 3D metrology
During operation of vehicles and structures, excessive transient loading can lead to reduced fatigue life and even
mechanical failure. It has been shown that when a structure undergoes a damaging sequence of events, such as those
occurring during a helicopter hard landing, the structural health of a specimen can be severely affected. In order to
effectively quantify damage and monitor the structural health of the specimen, experimental data is required across a
wide area of the helicopter. Within this paper the use of three-dimensional (3D) digital image correlation (DIC) and
dynamic photogrammetry (DP) is examined as a possible method to acquire the necessary data to perform structural
health monitoring in a non-obtrusive manner. DIC and DP are a non-contacting measurement techniques that utilizes a
stereo pair of digital cameras to track prescribed surface pattern or optical targets placed on the structure. The
approaches can provide global information about changes to the structure over the entire field of view. A scale
laboratory test is performed on a helicopter to simulate several loading scenarios. The changes in the structural shape
and strain field of the model helicopter fuselage as a direct result of the loadings are identified. The tests demonstrate
that this technique is a valid way to determine the damage inflicted on the structure due to an excessive applied loading or dynamic maneuver. Practical applications and common limitations of the technique are discussed.
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