PSI - Issue 52

Lucie Malíková et al. / Procedia Structural Integrity 52 (2024) 376–381 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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• specimen length, L = 24 mm; • specimen width, W = 4 mm; • corrosion pit depth, D = 0.1 to 1 mm; • corrosion pit length, LC = 4× D = 0.4 to 4 mm; • corrosion pit radius, RC = ( LC 2 +4 D 2 )/8 D ; • initial crack length, a = 0.1 to 1 mm; • initial crack inclination angle,  = -45 to +45°.

As it is obvious from Fig. 1b, the numerical model was two-dimensional. PLANE183 elements were used within ANSYS computational software to model the specimen. Plane strain conditions were assumed and mesh refinement along the corrosion pit as well as along the crack and especially at its tip was performed, see Fig. 2. Interaction integral method (implemented by means of the command CINT in ANSYS Mechanical APDL) was utilized to evaluate the basic fracture mechanics parameters, i.e. the stress intensity factor ranges  K I and  K II corresponding to loading mode I and II, respectively. Material model accepted within the finite element simulations was linear elastic with the constants E = 210 GPa (Young’s modulus) and  = 0.3 (Poisson’s ratio) correspondingly to basic HSS mechanical properties.

Fig. 2. Finite element mesh used within the numerical model for selected geometrical configuration.

2. Methodology and fracture criterion As mentioned above, linear elastic fracture mechanics (LEFM) concept, see e.g. Anderson (2017) was utilized to assess behavior of a short, angled fatigue crack propagating from the bottom of the corrosion pit. Because the crack is not perpendicular to the loading, both loading modes (I + II) are participating on controlling further crack propagation. To decide, in which direction the crack will deflect, the maximum tangential stress (MTS) criterion was applied. 2.1. Stress intensity factor range Stress intensity factor range can be defined as the level of the stress concentration at the crack tip during cyclic loading (similarly to the stress intensity factor derived for static loading). It represents the first singular term of the Williams expansion derived for stress tensor components approximation, see Williams (1957). When the most common one-parametric concept of the LEFM is taken into account, it is considered that the crack behavior is controlled by this only parameter.