PSI - Issue 42

Yuri Petrov et al. / Procedia Structural Integrity 42 (2022) 1040–1045 Yuri Petrov/ Structural Integrity Procedia 00 (2019) 000–000

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Fig. 3. Dependencies of load impulse on load amplitude for a crack in polycarbonate samples (Kalthoff and D.A. Shockey (1977)) and for a calibrated oscillator. Minima of the zero delay curves for the both problems are indicated. 4. Conclusions In this paper we showed that the fracture delay phenomenon which takes place when short loads are applied can be investigated using the incubation time fracture condition (ITFC). The ITFC implies that the macroscopic fracture is preceded by microscopic processes which require time to develop. As a rule, it is accompanied by a local relaxation process caused by microcracking, that is governed and measured by a certain characteristic time. This characteristic time is called the incubation time which is considered to be a material parameter. It was also shown that threshold loads need to be considered, if fundamental fracture effects are sought for, e.g. the fracture delay effect can be found when threshold loads are applied to the system. On the contrary, overloading hides this effect from observers. Moreover, the threshold loads can provide optimal fracture regimes. Acknowledgements

The study was supported by the RSF (Grant 22-11-00091). References

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