PSI - Issue 68

Aleksa Milovanović et al. / Procedia Structural Integrity 68 (2025) 922 – 928 A. Milovanović et al. / Structural Integrity Procedia 00 (2025) 000–000

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The conditional fracture toughness values are shown in Fig. 6-Left, with 100% and 70% results valid for the K IC estimation, and the 40% and 10% not. The 100% infill case has an average value of 2.27 MPa · m 1/2 , and the 70% infill case has an average of 2.04 MPa · m 1/2 (see table from the image). Next, the J max values are shown in Fig. 6-Right. Notably higher values from the other specimen groups are present in the 40% infill case, mainly due to high plasticity in the load-deflection response (see Fig. 4-Left). Here, the average value is 5.13 kJ · m -2 . The 100% and 70% specimens have similar J max values and the 10% has the lowest average of just 2.01 kJ · m -2 (see table from the image). Worth pointing out is that in all infill cases from the whole research (i.e., 10 infill groups, from 10% to 100%) the 40% infill case has the highest J max value in all three considered layer heights. Thus, one might expect that the largest J-R curve size and higher other J-integral values (such as J IC ) will be in the 40% infill case, but the extended paper will show the outcome.

Fig. 6. Charts supported with numerical results in the table below: Left- K Q values; Right- J max values.

The DIC dual-camera set device was employed, as in Milovanović et al. (2022c). Namely, the DIC cameras were used for monitoring the crack propagation and CTOD values of the SENBs’ front side. Five virtual strain gauges were evenly placed at the specimen ligament, circa 36 mm long, to monitor the strain during the test. These strain gauges are labeled as ‘’sections’’, starting from ‘’0’’ at the crack tip to ‘’4’’ at the other end of the ligament. The outputs are diagrams of the von Mises strain relative to section length, see Fig. 7. Here, two extreme cases are displayed, i.e.: one ‘’linear’’ specimen from the 100% infill (Fig. 7-Left) and one ‘’non-linear’’ from the 40% infill case (Fig. 7-Right). The diagrams were recorded from the last captured stage in the test.

Fig. 7. Von Mises strain values from virtual strain gauges for: Left- 100%; Right- 40% infill case.