PSI - Issue 75

Elena Sidorov et al. / Procedia Structural Integrity 75 (2025) 276–288 Elena Sidorov et al. / Structural Integrity Procedia (2025)

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Tab. 3. DIC analysis parameters

DIC software Image filtering

ZEISS CORRELATE (2025)

No filter 19 pixel 16 pixel bicubic Level 1

Subset size (facet size)

Step size (DIC point distance)

Sub-pixel displacement interpolation

Strain window

Virtual strain gauge size

+1,51

Strain formulation

Green-Lagrange

Post-filtering of strains Displacement noise-floor

No filter

approximately 20 µm

Strain noise-floor

approximately 0,1 % strain

Once the relevant spots are found, the pixels within an area of 3 by 3 mm around the spots are selected. The arithmetic mean of the pixel values is considered as the strain of the spot. Especially in case of very small strains, noise is unavoidable in DIC that may make it difficult to get reliable results. For analysing the measuring data, the noise was minimized through determining regression lines with MS Excel afterwards.

Fig. 6. Random speckle pattern (above) and full-field strain maps (below) at the back side of selected test specimens. Note: The visible black dot markings at the back side create a grid to facilitate the spots that corresponds with the strain gauge location at the front side.