PSI - Issue 30

A.A. Alexeev et al. / Procedia Structural Integrity 30 (2020) 1–5 A.A. Alexeev et al. / StructuralIntegrity Procedia 00 (2020) 000–000

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Velocity measurements showed that in the case of straight-line propagation, the crack velocity is 350-541 m/s, and when crack branching, the crack velocity is 679-746 m/s (Fig. 4).

Fig. 3. Crack branching during fracture of the vessel

These values of crack velocity in steel correlate with the test data of samples made of polymethylmethacrylate, where the crack branching velocity of a single crack is 500 m/s, with multiple branching of cracks with a parallel movement of the front of several cracks 750–920 m/s (Alexeev, 2017). Thus, these results show that the crack branching rates in polymers and steel coincide, and also show that the crack branching rate is a critical (limiting) crack propagation velocity, and energy entering the top of a moving crack is not spent on increasing the crack velocity, but on creating new cracks by branching (Alexeev, 2013).

Fig. 4. The crack velocity at various stages of propagation, branching cracks.