Sensitivity Analysis of a Damage Detection Method Through High-Resolution Photos on Various Statically Deflected Beams

In this manuscript, the authors deeply investigate and test a modern technique that allows the analysis of a structure starting from a photo to identify and locate damage present on it, rapidly and non-destructively without any physical interaction with the analyzed structure. The technique suitability is tested on four statically deformed beams, on which notches represent the defects. The core of the proposed method is the correlation between the curvature that each beam presents under load conditions and its flexural stiffness. The proposed methodology consists in taking a photo of the inflected beam; subsequently, the acquired photo is manipulated with specifically designed image processing tools, and the second derivative of the beam axis is estimated using two distinct numerical differentiator filters (Lanczos filter and Gaussian wavelets) along with suitable processing to reduce border distortions. The tests conducted demonstrate that it is possible, with an opportune static deflection amplitude, to accurately detect the position of the notch with the proposed procedure; a sensitivity analysis is also conducted by testing the procedure with different beam thicknesses, notch positions, and amplitude of the static deflection. Although the authors realize that the technique can generally require sensibly large displacements, the results seem promising.