PSI - Issue 76

Daniele Rigon et al. / Procedia Structural Integrity 76 (2026) 35–42

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Fig. 3. (a-c) Estimated maximum micro-notch depth ( S est

v , max ) as a function of sample size, showing convergence beyond 10 data points and less

than 5% deviation from measured value. (d) Gumbel probability plot of 50 S v , j values taken from Ti64 19 specimen.

Fig. 4. (a) Subsurface defect size ( √ area) vs. distance from as-built surface as measured by µ -CT. (b) Comparison between fatigue limit predictions based on maximum S mea v , max , i measured by OP and the subsurface defect with maximum size measured by CT.

Figure 4a reports the values of √ area of subsurface defects and their minimum distance from the as-built surface. According to Murakami’s guidelines Murakami (2019), a defect located at a distance from the surface that is smaller than its size can be considered a surface defect; otherwise, it should be regarded as an internal defect. Therefore, the highlighted defects in Figure 4a can generally be considered surface defects that can potentially interact with roughness.