PSI - Issue 68

Masayuki Arai et al. / Procedia Structural Integrity 68 (2025) 3–8 M. Arai et al. / Structural Integrity Procedia 00 (2025) 000–000

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Fig. 2. Geometry of CT specimen with the interlocking structure.

Fig. 3. Finite element model for the CT specimen.

2.2. Numerical results and discussion Table 1 shows the FE results for h = 0.0, 3.2, and 9.6 mm as representative results. The left side shows a contour plot of the equivalent stress, and the right side shows the crack propagation features. The crack propagates almost straight when ℎ = 0.0 mm. For ℎ = 3.2, stress concentration occurs at the kerakubi, and parts F and M slip along the interface of the sickle joint. When the tensile load is further increased, the crack propagates through the base material at the edge of the sickle joint in part M. For ℎ = 9.6 mm, a complex fracture pattern appears, and includes a crack initiated from the sickle-joint root of part F and tearing at the minimum cross section of the sickle joint. The FE results show that when the sickle-joint height ( ℎ ) is small, the deformation proceeds with a slip along the sickle-joint interface and crack formation, owing to the stress concentration at the kerakubi. As ℎ increases, stress concentration occurs at the smallest cross section of the kerakubi, leading to fracture. Fig. 4 shows the load–displacement curves obtained from the FE analysis. For ℎ = 0.0 mm, the load increases linearly as the displacement increases, and after the maximum load is reached, it suddenly drops and breaks. Compared with the crack propagation feature observed in the FE model, the maximum load corresponds to crack initiation at the tip of the pre-crack, and the load drop occurs by crack propagation. By introducing the interlocking structure, the load gradually increases with displacement, owing to slip deformation at the sickle-joint interface. After reaching its maximum value, the load gradually decreases with increasing displacement. The stepwise decrease in the load corresponds to the pullout at the sickle-joint interface, and to the continuous growth of the crack initiated at the sickle joint root. These results confirm that the load gradually increases, and that the elongation also increases by introducing a sickle-joint structure at the tip of the pre-crack.