Structural Health Monitoring by Laser Shearography: Experimental and Numerical Investigations
Non-destructive testing (NDT) is critical for many precision industries because it can provide important information about the structural health of critical components and systems. In addition, NDT can also identify situations that could potentially lead to critical failures. Specifically, NDT by optical methods have become popular because of their non-contact and non-invasive nature. Shearography is a high-resolution optical NDT method for identification and characterization of structural defects in components and has gained wide acceptance over the years; however, in practice, application of laser shearography for structural health monitoring requires loading the sample, which in some cases is not applicable or requires an experienced operator to properly perform structural testing. In this paper, a hybrid approach is proposed in which Finite Element Modeling (FEM) is used to simulate different loading conditions to obtain deformation data and in-turn, to obtain the simulated shearographic fringes. Different types of defects are embedded on the FE models and corresponding shearographic fringes are predicted. Correlating the defect and loading type to the predicted fringe pattern, in real shearographic measurements, different fringe patterns can be interpreted and classified. Also, camera calibration and image registration algorithms are used to project shearographic data onto the sample itself to locate and visualize the position of defects.
KeywordsFEM Fringe prediction NDT Shearography Structural health monitoring
The authors gratefully acknowledge the support provided by NIST program at Worcester Polytechnic Institute. We would also like to thank our colleagues at the CHSLT labs and Trilion Quality Systems.
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