PSI - Issue 60

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M Mohan Kumar et al. / Procedia Structural Integrity 60 (2024) 177–184 M Mohan Kumar et al. / Structural Integrity Procedia 00 (2024) 000 – 000

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(a) (c) Fig. 7: Von Mises stress around crack tip for (a) unstiffened panel (b) integral stiffened panel (c) riveted stiffened panel (b)

6. Conclusion: Stress analysis of the unstiffened and stiffened panels of a transport aircraft fuselage was performed in the presence of centre crack configuration. Stress intensity factor calculations were carried out for various incremental crack lengths across the width of the panel in both the types of stiffened panel. The stress intensity factor of the progressive crack decreases as it nears the stringers andgradually increases as it moves away fromthe vicinity of the strin gers. Due to the integral stiffening, higher stress intensity factor is observed in the integrally stiffened panel in comparison with the riveted stiffened panel, as the crack passes through the stringers. It may be observed that due to higher stresses around the progressive crack tip, failure in the integrally stiffened panel occurs when the half crack length progresses up to critical crack length of 225 mm which corresponds to critical stress intensity factor of 52.5 MPa √ m. However, in the riveted stiffened panel, stress intensity factors developed at the crack tip, are below the fracture toughness ( K IC ) of the material which is 54 MPa √ m. It is observedfromthe analysis results that the panelwith integralstiffener has low load sustaining capability compared to the riveted stiffened panel, whereas the riveted stiffened panel has better damage tolerant capability than the integral stiffened panel for the same applied loading conditions. Acknowledgements Authors would like to thank Head, Structural Integrity Division (SID) and Director, CSIR-NAL, for their support and encouragement during the course of this work and also for all those who have contributed directly or indirectly to this work. References [1] Gong Hai, Yi Bin, Wu Yunxin , Liao Zhiqi , Liu Yaoqiong and Du Fe. Integral Air-craft Wing Panels with Penetration Cracks: The Influence of Structural Parameters on the Stress Intensity Factor, Appl. Sci. 2020, 10, 4142; doi: 10.3390/app10124142. [2] Zhang, X.; Boscolo, M.; Figueroa-Gordon, D.; Allegri, G.; Irving, P.E. Fail-Safe Design of Integral Metallic Aircraft Structures Reinforced by Bonded Crack Retarders. Eng. Fract. Mech. 2009, 76, 114 – 133. [3] Grbovi´c, A.; Sedmak, A.; Kastratovi´c, G.; Petrašinovi´c, D.; Vidanovi´c, N.; Sghayer, A. Eect of laser Beam welded reinforcementon integralskin panelfatiguelife. Eng. Fail. Anal. 2019, 101, 383 – 393. [4] Moreira, P.; Castro, P. Fractographic analysis of fatigue crack growth in lightweight in -tegral stiffened panels. Int. J. of Struct. Integr. 2010, 1, 233 – 258. [5] C. C. Poe. Crack Propagation in Stiffened Panels, ASTM STP 486, 1971