Issue 78

G. Palomba et alii, Fracture and Structural Integrity, 78 (2026) 233-247; DOI: 10.3221/IGF-ESIS.78.14 and ε xx as transverse strain. As shown in Fig. 3, the transverse ( ε ₓₓ ) and longitudinal ( ε ᵧᵧ ) strain contours obtained at the ultimate load stage for the welded specimen highlight clear mechanical heterogeneity across the gauge length.

Figure 2: Example of speckle pattern, of the region of interest encompassing the gauge section of the specimens and of the elements grid. The central weld region exhibited markedly lower strain levels compared to the adjacent base material (BM), confirming that the weld metal (WM) acts as a locally stiffer and less deformable zone. This behavior is consistent with the refined grain structure and increased hardness measured in the WM, which are known to elevate yield strength at the cost of ductility. Notably, strain localization was not uniformly distributed across the specimen but rather concentrated near the interface between the heat-affected zone (HAZ) and the WM. This transition region exhibited elevated strain gradients, suggesting it may have a higher probability to serve as a preferential site for plastic instability, necking initiation, or fatigue crack nucleation under cyclic loading.

(a) (b) Figure 3: Digital Image Correlation (DIC) analysis derived strain contour for (a) transverse strain and (b) longitudinal strain. Fig. 4 and 5 show Digital Image Correlation strain maps during a tensile test of respectively a non-welded and a welded specimen. The engineering stress–strain responses for the non-welded and welded AISI 316L specimens are reported in Fig. 6. The non-welded (plain) samples display typical strain-hardening behaviour characteristic of austenitic stainless steels, exhibiting consistent yield strengths and ultimate tensile strengths across the three replicates, accompanied by relatively high uniform elongation exceedingly approximately 25%. In contrast, the welded specimens demonstrate comparable yield and ultimate tensile strength values to those of the base material (BM), indicating that the welding process did not significantly

237