DOI: 10.5176/2301-394X_ACE17.129

Authors: Niranjan Desai, Joel Poling, Gregor Fischer and Christos Georgakis

Abstract:

Structural health monitoring (SHM) assists engineers in maintaining structures, making them safer and more cost effective. Digital image correlation (DIC) techniques applied to SHM are non-contact, fast, and accurate techniques that are easy to apply. This investigation compared the accuracy of the smallest strain accurately measurable by the state-of-the-art DIC – based tools ARAMIS and iMETRUM, in a specimen moving out-of-plane. Initially undetected damage at low strains in connections of a realworld bridge motivated this investigation, whose detection would have restricted its spread, leading to lower repair costs. The study expands upon a preliminary study that determined the smallest strains measurable using the same DIC-based tools in a specimen that was not subjected to controlled out-of-plane movement. This initial study demonstrated that small out-of-plane specimen movements that inadvertently occurred even in controlled laboratory conditions led to noise in the DIC-based strain measurements. Hence, prior to implementing this technique in a real structure to detect small strains, it is desirable to determine the limits of out-of-plane specimen displacement within which it is practical to use this technique to measure strain. A cantilevered plate specimen was transversely loaded in the laboratory, and the longitudinal strain was measured at a selected location at different values of out-of-plane specimen displacement, using the DIC-based tools. The DIC strains were compared against those measured by traditional strain gauges. The smallest strains accurately measurable using both DIC-based tools, over a range of specimen out-of-plane displacement amplitudes, were determined.

Keywords: Structural Health Monitoring, Digital Image Correlation

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