Fatigue crack initiation and growth behavior of Ti–6Al–4V under non-proportional multiaxial loading

Low cycle fatigue life of Ti–6Al–4V alloy under non-proportional loading

“…The discrepancy between the actual a à and the a à cal may be due to the fact that Ti-6Al-4V has the HCP structure. In addition, the value a à =0.38 represents a significant life reduction due to nonproportional loading from the proportional loading, this life reduction has been explained in a previous study of observing the crack behavior of Ti-6Al-4V under non-proportional loading [19], crack initiation and propagation behaviors were clearly different between proportional loading (PP and TP) and non-proportional loading (CP). That is, the crack growth directions of PP and CP are perpendicular to the axial direction on the specimens, but that of TP turns to several directions on the specimen.…”

“…In addition, some studies about the fatigue property of Ti alloys have been reported [17,18]. Meanwhile, only a paper by the authors [19] has dealt with multiaxial low cycle fatigue crack behavior of Ti-6Al-4V.…”

A Review of the As-Built SLM Ti-6Al-4V Mechanical Properties towards Achieving Fatigue Resistant Designs

“…The complexity of the SLM microstructure presents some concerns with respect to how the crack propagates during both proportional and non-proportional loading. This is further complicated by non-proportional loading, since the principal stress and strain axes rotate during cycling, which not only actives more slip planes [83] but can also result in defects having an even greater influence than they would have in proportional loading. Moreover, the defects present in the material are likely to result in localised stress concentrations, causing shear stresses to promote slip and, therefore, lead to crack nucleation.…”

“…Other than the SLM acicular α martensite microstructure investigation by Fatemi et al [77], Ti-6Al-4V multiaxial fatigue investigations have considered mainly the wrought bimodal Ti-6Al-4V microstructure [83,[86][87][88]]. An understanding of the microstructural influence on the critical plane orientation is particularly important in the development of a fatigue resistant microstructure, since the underlying microstructure can have a significant influence over the fatigue fracture plane characteristic of the material [89].…”

Fatigue strength of severely notched specimens made of Ti–6Al–4V under multiaxial loading

“…With regard to multiaxial loading, the LCF behaviour of tubular specimens made of Ti–6Al–4V has been investigated by Hoshide et al ., focusing the analyses on proportional loading and the effect of microstructure, and by Nakamura et al ., who analysed the effect of out‐of‐phase loading. Regarding the HCF, the resistance of smooth specimens made of Ti–6Al–4V under multiaxial loading, both proportional and non‐proportional, has been studied by Kallmeyer et al ., who have also compared various multiaxial fatigue models to verify their suitability at estimating fatigue damage in this titanium alloy.…”