Issue 78

A. Sancak et alii, Fracture and Structural Integrity, 78 (2026) 186-206; DOI: 10.3221/IGF-ESIS.78.11

Figure 11: Stereomicroscope observations of seawater-exposed specimens after 30 days of immersion as a) group 7, b) group 9, c) group 10, d) group 11. The images compare fracture-surface morphology for specimens tested at 0 and 23 °C with different notch-timing conditions. The notch-timing specimens further indicate that the local condition around the notch and fractured ligament is important. In the pre-notched specimens, the notch-root region was directly exposed to seawater before impact testing, whereas in the post-corrosion-notched specimens the V-notch was introduced after immersion. The stereomicroscope images show visible differences in surface condition and fracture morphology between these groups. However, the absorbed impact energy did not change in a single monotonic direction with notch timing. This non-monotonic response suggests that notch timing should be considered together with local corrosion condition, test temperature and specimen-to-specimen material variability rather than as an independent controlling factor.

Figure 12: Stereomicroscope observations of selected reference and seawater-exposed Charpy specimens as a–b) group 1, c–d) group 10. The images highlight differences in fracture-surface morphology and surface degradation among the investigated conditions. Overall, the stereomicroscope observations support the quantitative Charpy results by showing temperature-dependent fracture path changes. Therefore, the stereomicroscope observations were considered together with the hardness measurements and near-fracture cross-sectional SEM examinations as complementary qualitative evidence. Taken together, these observations highlight macroscopic fracture-surface differences and local near-fracture microstructural variability among the selected specimens. However, they do not establish a direct causal relationship between the observed cross sectional features and the measured absorbed impact energy.

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