PSI - Issue 66

Akash Shit et al. / Procedia Structural Integrity 66 (2024) 247–255 Shit and Prakash/ Structural Integrity Procedia 00 (2025) 000–000

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3. Results and Discussion This study focuses on the influence of bi-axial load ratio on the effective Stress Intensity Factor (SIF) across various holes location in riveted joints. Under equi-biaxial loading conditions, the variation of the effective SIF with crack length is analyzed for the holes at location 1, 3, 4, and 5. 3.1. Variation of Effective SIF under Equi-biaxial Loading at Different Hole Location Under equi-biaxial loading (load ratio 1), the variation of the effective Stress Intensity Factor (SIF) with crack length at four locations (H1, H3, H4, and H5) in the left part of the strap plate connected with the Lozenge pattern riveted joint is presented in Figs. 3(a) and 3(b) for crack tip-1 and crack tip-2, respectively. Due to the symmetric positioning of H1 and H5, the SIF distribution with crack length is identical for both crack tips. The SIF gradually increases with crack length up to 40 mm at H1; beyond this point, the SIF begins to decrease due to the change in the orientation of the local crack tip. The effective SIF at crack tip-2 for the crack located at H3 follows a similar trend to H1 along the crack length. However, the effective SIF at crack tip-1 continuously increases with crack length, except for a slight decrease at 40 mm. The effective SIF is significantly lower at crack tip-1 compared to crack tip-2, possibly due to the stress flow alteration caused by the presence of H2 in front of crack tip-1. The percentage difference in effective SIF between crack tip-1 and tip-2 at H3 gradually increases with crack length, reaching a maximum of 107% at 40 mm, after which the difference decreases to approximately 10% at 50 mm crack length. Both crack tips at H4 and H5 in row 3 show a similar effective SIF distribution with crack length characterized by a gradual increase. At H4, for the initial 1 mm crack length, the effective SIF at tip-1 is 29% higher than at tip-2 due to the initial crack orientation. Subsequently, the effective SIF at tip-2 surpasses that at tip-1, with a peak 16% difference at 36 mm crack length. It is observed that each row of the Lozenge pattern riveted joint exhibits a unique variation in effective SIF with crack length. The holes within a specific row follow a consistent trend. However, at Hole-3, located in the middle row, the characteristics of SIF distribution with crack length is shown in Fig. 3 where the SIF distribution for crack tip-2 resembles that of row 1, while for crack tip-1, it mirrors the characteristics of row 3. a b

Hole ‐ 1

Hole ‐ 3

Hole ‐ 4

Hole ‐ 5

Hole ‐ 1

Hole ‐ 3

Hole ‐ 4

Hole ‐ 5

1000 1200 1400

1000 1200 1400

0 200 400 600 800 K_effective, MPa.mm^0.5

0 200 400 600 800 K_effective, MPa.mm^0.5

30 35 40 45 50 55

30 35 40 45 50 55

Crack length (2a) in mm

Crack length (2a) in mm

Fig. 3. Variation of K_effective under load Ratio-1 at different Hole locations of (a) Crack tip-1 (b) Crack tip-2 After analyzing the effective SIF at various locations of the 3-2-1 Lozenge pattern riveted joints under equi biaxial loading, it is noted that H1 is the most critical location. Figure 4 illustrates the percentage decrement of effective SIF at crack tip-1 for holes in rows 2 and 3 compared to H1 in row 1. At an initial crack length of 32 mm, the percentage decrement of effective SIF at H4 and H3 is nearly identical at approximately 34%. As crack length increases, the percentage difference at H4 exceeds that at H3. The maximum decrement of effective SIF with respect