The change in the geometry of a macrocrack in the process of its growth is a consequence of the mechanisms that occur under the effect of variable amplitude loads. Known solutions consider an absolutely sharp crack in a linearly elastic material, which leads to a singularity of stresses and accordingly to a tendency of infinite magnitudes of stresses in front of the crack. Well-known experimental studies show that the stresses in front of a crack can be several times higher than the yield strength of a material but still take final values. The paper analyzes the results of well-known studies on the behavior of a moving macrocrack in various stress-strain states. It is shown that the kinetics of the geometry of a growing crack differs noticeably from similar characteristics of a fixed crack, primarily due to the formation of a plastically deformed material on the crack sides. In the case of the implementation of a plane stress state in front of a crack the effect of the crack sides closing appears, significantly reducing the effective magnitude of the stress intensity factor and, accordingly, the crack growth rate. It is proposed to consider as a promising direction the transition to solving a threedimensional problem before the tip of the crack as is done in SY-models.
structural element, macrocrack, stress state, stress intensity factor, plastic zone
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