Fatigue Crack Growth in Titanium Alloys Under Cyclic Loading

The work is devoted to the study of the effect of regular cyclic loading on fatigue crack growth kinetics. Duration of fatigue crack growth of titanium alloys VT6 (α + β structure) and PT-3V (pseudo-α structure) under external cyclic loading at room temperature was investigated. Flat compact samples of type C(T) with a thickness of 5 mm were used according to the ASTM-E647 standard. The estimation results of the fatigue crack growth at a maximum load value of 3–5 kN and different asymmetries R = 0.1–0.7 are shown. Fractographic studies of crack growth were carried out. It was found that the kinetics of crack growth largely depends on the force parameters of variable loading and loading asymmetry. The experimental data on fatigue crack growth kinetics of a wide range of external loading were obtained. The analysis of the crack growth kinetics, depending on the properties of materials and the nature of variable external exposures, was carried out based on the study of the obtained fatigue fracture kinetics diagrams (henceforth FFKD) and fractographic features of crack development. The mechanisms of such crack behavior and modeling of the duration of its development are discussed. The effect of the asymmetry on crack growth is estimated. Modeling of the kinetics and duration of crack growth using the effective stress intensity factor (henceforth SIF), taking into account the method of “cycle-by-cycle” calculation of a crack length, is proposed. The comparative analysis of the calculated duration of crack growth and the experimental data obtained for these titanium alloys was carried out.