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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Fig. 3. Fracture surface of the hollow specimens at different loading conditions: (a, b) tension, (c, d) tension/torsion, (e, f) torsion.

From the crack front shape obtained in this way, the measurements of major semi-axis c and minor semi-axis a of growing surface crack can be obtained, using an optical instrumental microscope. In this study a is the distance of the deepest crack front(s) point from the specimen’s lateral surface, projected on the initial notch plane, c is the distance between a break through point and the specimen middle plane orthogonal to the initial notch plane (Fig. 1). As mentioned above, crack growth was monitored using the optical microscope and CMOD for tension and tension/torsion tests. Only the optical microscope measurements were used for torsion tests. The relationships between CMOD and crack length b on the free surface for both considered aluminum alloys under tension and tension/torsion tests are plotted in Fig. 4. A strong correlation was found between these two parameters for the tension and tension torsion tests and this information can be very useful for the verification of numerical simulation results under multiaxial stress states.

Fig. 4. Relationship between CMOD and crack length on the free surface of the hollow specimen under (a) tension and (b) tension/torsion.