Surface Stitching of a Wind Turbine Blade Using Digital Image Correlation
Advances in computing and camera technologies have greatly enhanced the utility of three dimensional (3D) digital image correlation (DIC) in the last several years. For example, 3D DIC is now being used as a tool to measure operational deflection shapes, full-field dynamic strain and discrete point tracking. Due to the line of sight requirements of stereo photogrammetry it may not be possible to measure every location required on a surface within a field of view allowed by a single camera pair. Therefore, there is a need to have the capability to stitch several fields of view together, providing a continuous measurement over the entire surface of a structure. This paper presents an approach to stitch several fields of view measured using 3D DIC, to provide full-field information of a Sandia National Laboratories CX-100 nine meter wind turbine blade. A loading test was performed on the cantilevered turbine blade with 16 separate fields of view captured in both loaded and unloaded conditions. The processed results provide full surface displacement and strain information of the CX-100 nine meter blade. These results indicate the potential of utilizing stitching to perform full surface static and dynamic measurement of structures.
KeywordsWind Turbine Digital Image Correlation Blade Surface Wind Turbine Blade Optical Target
The authors gratefully appreciate the financial support for this work provided by the Department of Energy (Grant # DE-EE001374), and thank the National Renewable Energy Laboratory for use of its test facilities and support from staff at the National Wind Technology Center namely Norman Hill and Bill Gage for assistance during testing. The authors also thank Mark Rumsey and Sandia National Laboratories for providing the test blade used in these experiments.
- 1.Helfrick M (2008) An investigation of 3D digital image correlation for structural health monitoring and vibration measurement. Masters thesis, University of Massachusetts LowellGoogle Scholar
- 2.Helfrick M, Niezrecki C (2007) An investigation of the use of 3-D optical measurements to perform structural health monitoring. Structural health monitoring 2007: quantification, validation and implementation. In: Proceedings of the sixth international workshop on structural health monitoring, Stanford, 11–13 Sept 2007Google Scholar
- 3.Helfrick M, Pingle P, Niezrecki C, Avitabile P (2009) Using full-field vibration measurement techniques for damage detection. In: Proceedings of the IMAC-XXVII, OrlandoGoogle Scholar
- 4.Helfrick M, Niezrecki C, Avitabile P (2008) 3D digital image correlation methods for full-field vibration measurement. In: Proceedings of the twenty-sixth international modal analysis conference, OrlandoGoogle Scholar
- 5.Warren C, Niezrecki C, Avitabile P (2009) Applications of digital image correlation and dynamic photogrammetry for rotating and non-rotating structures. In: Proceedings of the seventh international workshop on structural health monitoring, StanfordGoogle Scholar
- 6.Paulsen US, Erne O, Moeller T, Sanow G, Schmidt T (2009) Wind turbine operational and emergency stop measurements using point tracking videogrammetry. In: Proceedings of the 2009 SEM annual conference and exposition, Albuquerque, 4 June 2009Google Scholar
- 7.Johnson J, Hughes S, Van Dam J (2009) A stereo-videogrammetry system for monitoring wind turbine blade surfaces during structural testing. In: Proceedings of the 2009 ASME early career technical conference, Tuscaloosa, pp 1–10, 2–3 Oct 2009Google Scholar
- 8.GOM Optical Measuring Technologies (2007) ARAMIS: user manual—software. s.n., BraunschweigGoogle Scholar
- 9.Hugin – Panorama photo stitcher. http://hugin.sourceforge.net/. Last checked 20 June 2011