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Wind turbine blades are often subjected to static and dynamic testing to identify the performance levels of the blades. In general, strain gages are employed to capture strain data at discrete points. Recent advances in digital image correlation (DIC) and digital photogrammetry have allowed for new opportunities for blade inspection and structural health monitoring. DIC allows for imaging techniques to measure displacement values at various points on the structure. This displacement data is then used in conjunction with a finite element model to apply modal expansion techniques to obtain displacement values at each finite element degree of freedom for each time step of dynamic transient data. This technique is used to predict strain values at any point on the structure. This paper presents results obtained from dynamic testing at limited measurement locations to predict the full field dynamic strain for two structures evaluated. A major benefit to this approach is that strain values can be found at locations that are not in the measurement field of view, including on surfaces that are contained within the structure.

Modal testing is performed on wind turbine blades to provide information that is necessary for model updating and validation. In this work, a finite element model of a small wind turbine blade is developed and is used to perform dynamic stress–strain prediction using digital image correlation techniques. In order to assure that the model is appropriate for this work, a modal test is performed and correlated to the finite element model. Several blades are tested to identify the variability expected in the as-built configuration. This paper presents the test, analysis and correlation for this wind turbine blade.

Often times, wind turbine blades are subjected to static and dynamic testing to identify the performance levels that can be achieved for a particular configuration. These tests are a necessary part of the validation process. Typically, a variety of different static and dynamic measurements are made using a variety of different transducers. Typically, only a handful of strain gages are deployed to capture strain information. Recent advances in digital image correlation (DIC) and dynamic photogrammetry (DP) have allowed new opportunities for blade inspection, structural health monitoring, and full-field vibration testing. The primary benefit to using DIC is that the measurement approach is not limited to identifying the displacement or strain at only a few discrete measurement locations, but instead makes full-field surface measurements possible. These techniques are currently being explored on several wind turbine blade applications and can provide a wealth of additional information that was previously unobtainable. This paper, which is the first part of a two part paper, presents the static strain measurements and calibration of the system overall. The strain distribution along the length of the structure is compared to the finite element model. The data analysis is used to assure that the model is calibrated for the dynamic testing results; dynamic testing results are presented in the second part of this paper.

Often times, wind turbine blades are subjected to static and dynamic testing to identify the performance levels that can be achieved for a particular configuration. Many times only a handful of strain gages are deployed to capture that information.