PSI - Issue 39

Aljaž Ignatijev et al. / Procedia Structural Integrity 39 (2022) 89 – 97 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 4. Fatigue crack initiation period (Load case 3).

2.4. Crack propagation period In the computational model for the crack growth the Paris law was used. The needed fracture mechanics parameters were taken from previous work by Šori (2016), see Table 4. In the framework of the Ansys software, a crack was created to analyse the fracture behaviour using the "Arbitrary Crack" and "Smart Crack Growth" tools.

Table 4. Fracture mechanics properties of Cu–Ni–Mo sintered steel in hardened states. Parameter Symbol Value Paris law coefficient C [( mm⁄cycle)/(MPa√m) 7,396 ] 7.824∙10 -13 Paris law exponent m [−] 7.396 Threshold stress intensity factor ∆ K th [ MPa√m ] 5.240 Critical stress intensity factor K Ic [ MPa√m ] 25.45

The initial crack length was 0.375 mm and was determinate with equation (3) from literature by Dowling (1999), where ρ defines the radius of the root of the tooth, which equals 2.5 mm. The crack was defined at the maximum bending stress in the tooth root perpendicular to the surface, see Fig. 5. The size of the finite elements around the crack’s tip was 0.05 mm and was meshed automatically. 0 ≈ (0.1 … 0.2) ⋅ (3) For each substep, the Ansys calculates a new crack increment. Thus, it was possible to monitor the equivalent stress intensity factor range. Fig. 5 shows the equivalent von Mises stress field at the initial length of the crack for load case