Issue 77

T. Jiao et alii, Fracture and Structural Integrity, 77 (2026) 362-385; DOI: 10.3221/IGF-ESIS.77.21

(b) tunnel defects

(c) LOP defects Figure 2: Microstructural characteristics of defects in FSW joints: (a) oxide inclusion defects; (b) tunnel defects; (c) LOP defects. Fatigue specimens were cut from the welded plates (sound joints and three types of defective joints) according to the shape and dimensions shown in Fig. 3. The specimen length direction was aligned with the material rolling direction. The weld center was positioned at the axial center of the specimen. To ensure consistent surface conditions, after removing flash from the weld surface, the specimen surfaces were polished along the rolling direction using sandpaper until the surface roughness of the weld surface reached Ra 3.2. The weld root was left in its original state without machining or surface treatment to simulate the possible stress concentration and defect effects at the root in actual structures.

Figure 3: Fatigue test specimen configuration for FSW joints (unit: mm).

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