PSI - Issue 18

Prokhorov A. et al. / Procedia Structural Integrity 18 (2019) 802–808 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Each test includes number of loading impulses. The duration of the impulse was determined by the time when the specimen temperature is less than 80 0 C. We analyzed each impulse based on discrete Fourier transform. The discrete Fourier analysis of signal shown that main frequency (700 Hz, fig 5a) and second harmonic (1400 Hz, fig 5b) of induced signal increasing during the experiment and have a maximum when the fracture of the specimen is rapidly evolve. (a) (b)

Fig. 5. (a) 700 Hz amplitude diagram during experimental. (b) 1400 Hz amplitude diagram during experimental.

During each tests the temperature of the specimen surface were recorded and analyzed. Characteristic temperature rate on each impulse were calculated using finite-difference method in the middle of the impulse. It is shown that each loading impulse temperature evolution has a different dynamic (fig. 6) which is also may be associated with damage evolution. All of presented diagram shown three stages of process evolution: initial stage (1-50 impulse), stable process (50 - 1000 impulse) and rapid increasing (1000-1500 impulse).

Fig. 6. Temperature rate diagram.