Analysis of bifurcatial transitions during subcritical fatigue crack growth

Combination of synergetic and fracture mechanics approaches has been demonstrated for investigation into cracking resistance of (α+β) - titanium alloys. It has been shown that a threshold rate of crack propagation is a fundamental invariant parameter controlling fatigue crack instability in metals. It correlates with change of fracture micromechanisms of break away at subcritical crack growth. The threshold rate proves to be possible within the certain range of stress intensity factors which in turn depends on external loading conditions. This dependence has allowed one to determine three points of bifurcate instability of crack on kinetic diagram of fatigue fracture. The existance of these points suggests that the change of energy dissipation mechanisms and as a result the change of fracture mechanism take place