PSI - Issue 75

John Hock Lye Pang et al. / Procedia Structural Integrity 75 (2025) 29–34 Author name / Structural Integrity Procedia (2025)

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1 exhibited surface-connected crack initiation, as highlighted by the orange-circled area in Figure 4 (a3). In contrast, the specimen post-treated with Sequence 2, which underwent additional shot peening process, showed crack initiation from a subsurface region, as indicated in Figure 4 (b3). Furthermore, a visible fatigue crack that extended from the surface without leading to complete fracture was observed in Figure 4 (b1). This observation suggests that shot peening effectively suppressed surface crack propagation. The change in crack initiation sites is consistent with the prolonged fatigue life observed with Sequence 2.

Figure 4 Fracture surface analysis of fatigue specimens processed by two post-treatment sequences (stress range: 390 MPa).

Figure 5 Surface roughness measurement of the post-treated fatigue specimens used for fatigue testing under 390 MPa