PSI - Issue 37

A. Vshivkov et al. / Procedia Structural Integrity 37 (2022) 570–575 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3. Experimental results

The figure 2 shows experimentally obtained time dependences of the crack length and heat flux. Two different types of heat flux behavior during crack propagation could be distinguished. At the beginning of experiment the heat flux remains practically constant, despite the fact that the crack length is gradually increasing. When crack length reaches about 9 mm, the heat flux deviates from the constant value, and then demonstrates an avalanche-like growth up to the fracture moment of specimens. The time moment when the heat flux begins to deviate from the linear trajectory is marked by red circles.

a)

b)

Fig. 2. Crack length (a) and heat flux (b) during fatigue test.

The characteristic kinetic diagram of fatigue fracture for different load level is presented in figure 3. The crack propagation corresponds the Paris low. The form of typical hysteresis loops in force-displacement coordinates are presented in figure 4. It illustrates data at the beginning of the experiment, at the point of transition from a constant heat flux to an avalanche-like growth, and at the final stage of deformation. With the development of the crack, the size of the hysteresis loop increases. The value of the plastic work was further estimated by the loop area.