PSI - Issue 39

Hithendra Karakampalle et al. / Procedia Structural Integrity 39 (2022) 711–721 Author name / Structural Integrity Procedia 00 (2021) 000–000

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2. Methodology Numerical estimation of stress intensity factor using Finite Element Analysis is considered as the methodology of this study. The crack is assumed to propagate along the defined path, which is plane perpendicular to the direction of loading. Three specific cases have been considered: First one was the study of crack emanating from rivet joint at one end of the strap plate and propagating up to the joint at the other extreme end (Fig. 2). The change in Stress Intensity Factor (SIF) in mode I (K I ) at both the crack tips was estimated. Simulations were run at various levels of interference and the best interference level at which SIFs are the minimum was identified.

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Fig. 2. Case 1: Crack propagating from L3 towards L1: (a) Notation of joints and initial crack size; (b) crack tips; (c), (d), (e) crack propagation; (f) final crack size. The second aspect of the study deals with the crack emanating from the joint at the center and propagating towards the joints at the two extremes, symmetrically, as shown in Fig. 3. Variation in the SIFs during the propagation of crack for different levels of rivet-hole interference was recorded and analysed. In addition, variation of stresses at joint L2 were studied and based on these stresses, an attempt was made to relate the loss in interference due to the increase in the crack size to the stress at the joint by comparing joint with higher crack length at higher interference with that of the joint with smaller crack at lower interference. a b c d

Fig. 3. Case 2: Crack propagating from L2 towards L1 and L3 : (a) plate without crack; (b) Initial crack 2a=6 at L2; (c) crack propagation; (d) final crack size

The third aspect of the study deals with variation of the SIFs at the crack and the stresses at the centrally located joint, in the presence of additional cracks at the joints on either side of it (Fig. 4). Multiple combinations of crack sizes at different interference levels were studied to identify the most beneficial interference. Given the applicability of the work to pin joints as well, henceforth, the term ‘pin’ is used interchangeably with ‘rivet’.