Assessment of electronic shearography for structural inspection |
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Authors: | A K Maji D Satpathi S Zawaydeh |
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Institution: | (1) Department of Civil Engineering, University of New Mexico, 87131 Albuquerque, NM;(2) Department of Civil Engineering, University of New Mexico, 87131 Albuquerque, NM |
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Abstract: | Electronic shearography (ES), a laser interferometry technique, has the potential for large-scale structural inspection and
for identifying cracks and strain anomalies. A system based on this technology could possibly be used for noninvasive inspection
of structures with high insensitivity and robustness. One major problem is the existence of largerigid body motions in typical
engineering structures such as bridges and high-rise buildings. These rigid-body motions are large enough to cause a complete
decorrelation of the characteristic speckle pattern that is obtained by illuminating the object surface. This nullifies any
possibility of interference between speckled images obtained at different stages of loading, as is necessary for interferometry
applications. A systematic study was conducted to characterize the speckle pattern obtained from typical civil structures
as a function of the illumination and imaging system. Experiments were carried out to quantify speckle decorrelation as a
function of object motion and instrumentation characteristics. A fracture mechanics based finite element (FEM) analysis was
carried out on an existing fractured bridge to determine the strains and displacements. The results of these studies were
subsequently used to define the parameters of a structural inspection system based on ES for field applications. |
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Keywords: | |
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