PSI - Issue 71

Abdul Khader Jilani Shaik et al. / Procedia Structural Integrity 71 (2025) 42–49

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6 Fatigue crack growth study in standard ASTM C (T) specimen To assess the accuracy of the numerical simulation methodology adopted, a simulation model of ASTM C(T) Specimen is created, whose SIF values can be computed from standard equations. The SIF values calculated from the FEM are validated against the corresponding SIF values of the standard ASTM Compact (Tensile) C(T) specimen according to ASTM E-1820-08a . The stress plot at the maximum load of 60 kN is depicted in Fig. 7. Additionally, Fig. 7 presents the crack growth analysis, illustrating the details of the crack extension phenomenon.

Fig. 7 Crack extension phenomenon in C (T) Specimen (maximum load 60 kN)

7 Fatigue Crack Growth Studies In the investigation of Fatigue Crack Growth, a pre-existing crack of known length (1.55 mm or 0.06 in) is introduced at a high peak stress location on a Lug, and subsequent fatigue crack growth analysis is undertaken to assess the operational life of the joint with this predetermined crack. Refer Fig. 8 (a) and Fig 8(b) . As a part of the investigation, a numerical simulation model has been developed based on the Unstructured Meshing Method (UMM) and Separating, Morphing, Adaptive, and Remeshing Technology (SMART). The SMART facilitates automatic updates to the mesh, accommodating alterations in crack geometry due to crack growth at each solution step. Unlike XFEM, SMART demonstrates efficient scalability for larger problems, as re-meshing is confined to a localized area surrounding the crack tip during each iteration. This innovative and novel approach is adopted to conduct nonlinear Fatigue Crack Growth analysis for a single-through crack and symmetric two cracks on the Lug Hole. Upon identification of high peak stress, a semi-elliptical crack is induced on the Bush. The Stress Intensity Factor (SIF) of the crack front and the magnitude of SIF at each stage of crack extension are carefully examined.

Fig. 8(a) Semi-elliptical Crack on the Bush.

8 (b) Geometry of the lug (through, single/Symmetric cracks [8]).

8 Comparative study of Simulation Results with analytical solutions The Stress Intensity Factor (SIF) KI, derived from the finite element method (FEM) under Mode I loading, was compared to analytical formulations for a semi-elliptical crack from S. Boljanović et al (2016). The 2.5% difference between the FEM and analytical solutions indicates satisfactory agreement. These equations, used for calculating SIF KI based on crack geometry, are detailed in S. Boljanović et al (2016). The estimated SIF from these equations is also presented below: = √ ( , , , , , ) (2) =√ + + (3) Shape factor for an ellipse, = + . ( ) . ;( )> (4)