1 April 2016 Terahertz ISAR and x-ray imaging of wind turbine blade structures
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Abstract
During the manufacture of wind turbine blades, internal defects can form which negatively affect their structural integrity and may lead to premature failure. The purpose of this research was to conduct preliminary testing of nondestructive evaluation techniques that have the potential to scale up to larger areas. The techniques investigated were: Terahertz frequency fully-polarimetric inverse synthetic aperture radar (ISAR), and x-ray imaging. The terahertz ISAR technique employed standard polarimetric radar cross-section processing, and additionally applied an optimized polarimetry transformation known as the Euler transformation. Also, image back-rotation and compositing algorithms were used to combine multiple ISAR images into a single image to aid in defect detection. ISAR data were collected using a frequency modulated continuous wave 100 GHz radar system. The x-ray technique utilized a commercial airport cargo x-ray scanner. Multiple fiberglass samples with defects representative of manufacturing wind turbine blade defects were investigated using each of the techniques. Out-of-plane defects and resin dry patches were the primary defects of interest in these samples. Images were created of each sample using each of the techniques. Comparing these images with defect diagrams of the samples indicated that these techniques could effectively indicate the presence of certain defects.
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Robert Martin, Christopher S. Baird, Robert H. Giles, Christopher Niezrecki, "Terahertz ISAR and x-ray imaging of wind turbine blade structures", Proc. SPIE 9806, Smart Materials and Nondestructive Evaluation for Energy Systems 2016, 98060I (1 April 2016); doi: 10.1117/12.2218616; https://doi.org/10.1117/12.2218616
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