PSI - Issue 76

Christina Mamagkinidou et al. / Procedia Structural Integrity 76 (2026) 82–88

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applying the trapezoidal rule for Eq. (1) between each measurement step. The resulting corrected residual stress profiles are presented with green diamond symbols in Fig. 3. The values computed with this method consistently predict higher tensile stresses in the central region and less compressive stresses at the intermediate regions, compared to the as-measured data in the rolling direction. The resulting profile perpendicular to the rolling direction shows slight tensile residual stresses over an extended region at the centre, reasonably compensating for the high compressive surface residual stresses very close to the surface.

Fig. 3. As-measured and corrected residual stress profiles in (a) rolling; and (b) perpendicular to rolling direction.

This evaluation underscores the importance of selecting an appropriate correction model when interpreting through-thickness X-ray diffraction residual stress data acquired with material layer removal techniques. 3.2. Comparison between crack initiation locations and residual stress distribution FE-SEM images of representative fracture surfaces with surface and interior failure are shown in Fig. 4(a) and (b), respectively. EDS analyses confirmed that fatigue cracks consistently initiated at titanium nitride (TiN) inclusions and agglomerates.

Fig. 4. Fracture surfaces of specimens tested at (a) σ a = 750 MPa, N f = 2.29×10

6 cycles; (b) σ

a = 550 MPa, N f =1.95×10

8 cycles.