PSI - Issue 39

R. Yarullin et al. / Procedia Structural Integrity 39 (2022) 364–378 Author name / Structural Integrity Procedia 00 (2021) 000–000

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4. Results and discussion In this section, the comparisons of numerical simulation with experimental results are presented. 4.1. Crack paths comparison First of all, in Fig. 13, a comparisons of fatigue crack growth surfaces predicted by the MTS criteria with corresponding experimental surfaces, are depicted for different loading conditions, obtaining a sound agreement between numerical and experimental crack paths. In particular, the numerical crack path is perfectly symmetric and well approximates the experimental crack surface kinking; a higher kink angle is observed in the case of pure torsion loading condition with respect to combined tension-torsion.

Fig. 13. Numerical and experimental crack paths comparison under (a) tension/torsion and (b) torsion loading conditions.

4.2. CMOD measurements comparison The second part of comparisons is referred to CMOD measurement vs crack length on the free surface as for numerical simulation and experimental results. As was mentioned above, CMOD gage was used for tension and tension/torsion tests. CMOD is directly related with compliance of the specimen and depends on the crack size, geometry of the specimen, the elastic modulus and the applied force. All compliance-crack size relationships are applicable only for the measurement locations on the specimen for which they were developed. In this study CMOD measurement was used for the verification of numerical simulation results under multiaxial stress states. In Fig. 14 the comparisons of numerical and experimental CMOD are presented for tension and tension/torsion loading