An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
There has been a renewed interest of late in the mechanisms responsible for the influence of the load ratio, R, and the maximum stress intensity, K max, on the threshold for fatigue-crack growth, ΔK th. While mechanistic explanations in the past have largely focused on the role of crack closure, it is certainly not the only mechanism by which K max influences ΔK th. In this work, we examine the effect of a wide range of loading frequencies (ν=50–1000 Hz) and load ratios (R=0.10–0.95) on fatigue-crack propagation and threshold behavior in a Ti–6Al–4V turbine blade alloy consisting of ∼60 vol% primary-α and ∼40 vol% lamellar α+β. The data presented in this paper indicate that at K max values above 6 MPa√m (R>0.5), where macroscopic crack closure is no longer detected in this alloy, ΔK th decreases approximately linearly with increasing K max. This result is discussed in terms of possible mechanistic explanations, including sustained-load cracking, microscopic near-tip closure, and static fracture modes, based on considerations of experimental evidence from both the current study and the literature.
