The kinetics of a macrocrack is a consequence of the mechanisms that occur in the immediate vicinity of its tip when the structural element is exposed to variable amplitude loads. Analysis of the literature indicates a significant interest of investigators to the question of macrocrack growth under irregular loading, which is explained by both practical expediency and simple interest in the nature of the phenomenon of fatigue failure. It was found that the crack growth rate is influenced not only by the amplitude of the load, but also by the history (sequence) of their impact. Due to different combinations of values and amplitudes of loads and their sequence, an opposite result is possible, leading to both a slowdown and an increase in the crack velocity. In the first part of the paper, the main attention is paid to the possible mechanisms occurring during the instability of the crack in the immediate vicinity of its tip. In the second part of the article the classification of irregular loads with corresponding consequences on the fracture kinetics will be given.
macrocrack, crack growth rate, structural element, stress intensity factor
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