PSI - Issue 28

Mohamed Ali Bouaziz et al. / Procedia Structural Integrity 28 (2020) 1039–1046 M.A. BOUAZIZ et al / Structural Integrity Procedia 00 (2019) 000–000

1042

4

was noticed on the surface of the material. The cracking pattern at the surface differed from one test to the other (Figure 2). The optical images acquired during the in-situ tensile tests allowed for a qualitative analysis of the local deformation of the material surface. Figure 2 illustrates the main local features at the specimen surface when failure occurred for both tested samples. In the first one (50 µm sample), the crack extended in two directions forming a Y shape over a relatively large distance (~ 750 µm) even though the load to failure was very low. Conversely, the 125 µm specimen experienced limited crack growth. One can also notice that, as shown by the images, the speckle patterns held up until specimen failure, which proved that the deposition technique adopted herein was well suited to this kind of material. Therefore, microscopic kinematic fields obtained by digital image correlation were measured.

(a)

(b)

Fig. 2. Last deformed configurations of the material surface prior to failure. (a) Sample with 50 µm layer thickness. (b) Sample with 125 µm layer thickness. 3. Kinematic field measurement DIC provides displacement fields (Sutton et al. 2009). From images of the surface in reference and deformed states, displacement vectors are retrieved by registering subsets in the reference and deformed images for local analyses. DIC resolutions are now sufficient to analyse experiments performed at various scales ( Sutton et al. 1999; Forquin et al. 2004). In the present study, the FE-based DIC code Correli 3.0 (Leclerc et al. 2015) was used to register the microscopic images acquired during the tests (Marae-Djouda et al. 2020a). Table 2 summarizes the DIC parameter sets used for both tests.