An approach based on macro-fiber composite transducer rosettes and ultrasonic guided waves is proposed for damage location in plate-like structures. By using the directivity behaviour of the three macro-fiber composite sensors in each rosette, the direction of an incoming wave generated by scattering from damage can be estimated without knowledge of the wave velocity in the structure. Two rosettes suffice to identify the location of a scatterer in a planar structure. The technique does not have the drawbacks of time-of-flight triangulation, requiring information on wave velocity that complicates the damage location when testing anisotropic materials, tapered sections or any structure under temperature fluctuations. The effectiveness of the piezoelectric rosette method is tested experimentally on an aluminium plate with a simulated damage subjected to temperature variation.
Delaminations are a common type of defect that occurs in composite structures such as wind turbine blades. In this study, a nondestructive testing technique based on Lock-In Thermography is proposed to detect skin-skin delaminations and skin-core delaminations present in a 9-m CX-100 wind turbine blade. A set of image processing algorithms and multivariate outlier analysis were used in conjunction with the classical Lock-In Thermography technique to counter the ''blind frequency'' effects and to improve the defect contrast. Receiver operating characteristic curves were used to quantify the gains obtained by using multivariate outlier analysis. Experiments were performed on a set of 16 defects of various sizes that were incorporated during the construction of the CX-100 wind turbine blade at different locations and depths.
The wind energy industry is rapidly growing in order to meet the increasing world energy demands as well as the need for clean and renewable energy sources. With the goal to explore new technologies and innovations which could help potentially improve the efficiency and effectiveness of wind energy, the NDE/SHM laboratory at UCSD acquired a unique wind turbine blade that will be used for performing several research projects related to wind turbine blade technology and non-destructive inspection techniques. The blade was built using the CX-100 design developed by TPI Composites, Inc. and Sandia National Laboratory (SNL). The 9-m blade was constructed with several embedded defects that represent the most common manufacturing defects typically found, such as out-of-plane waviness, composite delamination, and adhesive disbond. The defects were embedded during the manufacturing process by using similar methods developed by both TPI and SNL for simulating actual defect characteristics. Though the blade is small in comparison to the average utility sized blade of around 40 meters, the blade features similar materials and manufacturing methods, allowing for several inspections techniques to be studied on a representative platform. The inspection techniques include advanced infrared thermography and other guided wave techniques.
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