Issue 75

M. L. Bartolomei et alii, Fracture and Structural Integrity, 75 (2026) 35-45; DOI: 10.3221/IGF-ESIS.75.04

(a) (b) Figure 8: Characteristic residual strains patterns in specimens treated with a spot of D2 mm and a power density of 12.74 GW/cm² for specimens along the printing direction (a), along the build direction (b). A positive value of the relief strains indicates the presence of compressive residual stresses [19]. In general, for all treatment regimes, compressive stresses are observed at a depth of up to 1 mm, with the maximum amplitude at a depth of approximately 0.2 – 0.4 mm. Figs. 9 and 10 show the dependences of the total strain and the maximum relief strain on the laser pulse power density for specimens along the printing direction and along the build direction processed with a square beam (1x1) and a round beam (D2).

(a) (b) Figure 9: The relationship between the relief strains and the laser pulse power density for specimens along the printing direction (a), along the build direction (b).

(a) (b) Figure 10: The relationship between the maximum residual strains and the laser pulse power density for specimens along the printing direction (a), along the build direction (b). For specimens along the build direction, a more pronounced dependence of strain on the laser pulse power density is observed. For specimens along the printing direction, exposure with a square beam yields a better effect. This is likely due to the initial properties of the specimens and is related to the direction of the workpiece growing. Relief strains increase nonlinearly with the growth of the laser pulse power density. At power densities above 12-15 GW/cm², this growth is no longer as evident. The graphs of residual stress dependence on depth show similar patterns as those for residual strains, see Fig. 11.

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