Probabilistic fatigue-life assessment model for laser-welded Ti-6Al-4V butt joints in the high-cycle fatigue regime

The microstructure, mechanical, and fatigue behaviours of MAG welded G20Mn5 cast steel

“…HCF lifetime curves can be formulated by using the statistic method based on the International Institute of Welding Society combined with standard backwards statistical inference method . The relation of nominal stress range Δ σ with the number of cycles to failure N f can thus be expressed by the fatigue S ‐ N diagram: in which C and m are the material constants by the least‐squares method.…”

Simulation of fatigue small crack growth in additive manufactured Ti–6Al–4V material

“…does not vary with increasing crack length. Based on the conclusions made by Fomin et al [22], their proposed small crack growth model takes into account the varying (K eff ) th as a function of crack length '2a' and seems to be more accurate. • For AM Ti-6AL-4V model, we have not got the sufficient test data to develop the 'cyclic R-curve' and it should be looked into as part of the future research study.…”

“…A more accurate p value is required via the HCF tests on AM Ti-6Al-4V material. Fomin et al [22] have derived the p value by performing a regression analysis on the weld fatigue test data in HCF regime. This is expected to improve the fatigue life predictions in the HCF regime [22].…”

“…From a recently publication, Fomin et al [22] in their research have proposed a fatigue life assessment model which considers the effects of small cracks for laser-welded Ti-6Al-4V butt joints in HCF regime. Their proposed small crack growth model considered the 'cyclic R-curve' as a mean to reflect the reduced threshold value and the crack length dependent K th (a) for small cracks.…”

“…They suggested that by using the 'cyclic R-curve', the small crack effects can be analysed by introducing the dependence K th (a) in the crack growth equation. The construction of 'cyclic R-curve' comes with challenges and, as suggested by Fomin et al [22] in their simple approach to construct the 'cyclic R-curve' for internal cracks, it requires the knowledge of the intrinsic effective threshold stress intensity factor (( K eff ) th ) for small cracks, the fatigue endurance limit of the material and the threshold stress intensity for the long cracks ( K th_LC ). Furthermore, to construct a 'cyclic R-curve' there are other approaches outlined by Zerbst et al [23,24], which includes the experimentbased techniques and also the approaches utilising the Kitagawa-Takahashi diagram [25] and the Murakami' model of square root of the area of small surface cracks [26].…”