Chapter 20 Structural Health Monitoring by Laser Shearography: Experimental and Numerical Investigations Xiaoran Chen, Morteza Khaleghi, Ivo Dobrev, Weiyuan Tie, and Cosme Furlong Abstract 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. Keywords FEM • Fringe prediction • NDT • Shearography • Structural health monitoring 20.1 Introduction This paper focuses on our recent progress in developing a non-destructive procedure based on combination of Finite Element Modeling (FEM), fringe prediction, and laser shearography to facilitate rapid defect detection for structural health monitoring. More specifically, in order to improve the process of finding defects by engineers who have limited shearography experience, a hybrid approach is proposed in which by simulating different loading conditions using FEM, corresponding shearographic fringe patterns are predicted to optimize shearography setup and achieve high sensitivity of the measurements. Additionally, a multimedia projector is used to project shearographic results onto the real surface of the object of interest. By using this approach, inspectors would have a better understanding of how to apply load to the sample by viewing the simulated deformation results of the sample. Thus, the inspector would have a better idea of how to induce the desired deformation in real testing. X. Chen (*) • M. Khaleghi • I. Dobrev • W. Tie • C. Furlong Mechanical Engineering Department, Center for Holographic Studies and Laser micro-mechaTronics (CHSLT), Worcester Polytechnic Institute, Worcester, MA 01609, USA e-mail: xchen2@wpi.edu N. Sottos et al. (eds.), Experimental and Applied Mechanics, Volume 6: Proceedings of the 2014 Annual Conference on Experimental and Applied Mechanics, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-06989-0_20, #The Society for Experimental Mechanics, Inc. 2015 149
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