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Experimental Investigation of the Relationship Between Finite Element Modeling and Digital Image Correlation

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Nmair, Nicole

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Abstract

This thesis investigates the comparison between the behavior of a structure modeled in a finite element (FE) software to the behavior captured using Digital Image Correlation (DIC). This experiment opens the gateway to quicker and easier structural assessments of the nation’s infrastructure through the use of DIC, a research area that requires further investigation. Through experimental analysis, the ability of DIC to be used as a finite element calibration tool was tested. Comparisons were completed by analyzing and comparing the behavior of a fixed-fixed aluminum frame under varying static loads at the midspan of the beam. Two structural parameters were assessed in the comparative analysis including the structures response strain and deflection. Through the analysis of the deflection, an adequate comparison was concluded between DIC and the FE model, with average absolute differences in deflection between 0.004866 and 0.007075 inches. However, the structures strain response consisted of high error in the DIC strains resulting in unsuccessful comparisons between DIC and the FE model. These errors are predicted to have been caused by vibration in the system during loading, noise caused by high light reflectivity, construction error, and primarily, speckle pattern inadequacy. Since the deflection results were deemed feasible, Euler-Bernoulli theory was used to derive strain equations from DIC deflections, resulting in viable strain results for the structure. Overall, DIC’s ability to be used as a finite element model updating tool was confirmed yet requires further investigation into optimization methods for model parameter updating. Through this research, a better understanding of the limitations of the DIC was investigated, providing recommendations on the method of initial calibration between DIC and FE software.

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Digital Image Correlation, Structural health monitoring, Full field measurements, Finite element model updating, Finite element modeling

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