The developed method of recording current values of crack tip opening
displacement made it possible to reliably establish the instant when the “material” contact
between the borders of a fatigue crack near its tip in a tension half-cycle ceases and the upper
time limit after which the phenomenon of contact does not occur again, as well as to develop
experimentally fatigue crack growth criteria. The phenomenon of “material” contact is
evidenced by the presence of residual compressive stresses on the fatigue crack borders near
the tip during fracture, which impede the crack propagation in the passive part of the stress
cycle. Analysis of the revealed regularities in the fatigue crack propagation, changes in its
kinetic diagrams and the upper time limits of the contact phenomena due to various factors,
and existing formulas for crack growth rate calculations combined with the criteria and
approaches developed enabled reliable description of the fatigue crack propagation kinetics
and determination of the crack growth rate, life, and fracture types, as well as establishing the
relation between time-dependent local parameters of stress- and strain-based fracture criteria,
which accounts for the effect of any factors, their values lying in a wide range, which cause
elastic-plastic deformation of structural materials, on the fracture process
