Analysis of strain-life fatigue parameters and behaviour of different groups of metallic materials

Strain-life fatigue parameters of unalloyed steels, low-alloy steels, high-alloy steels, aluminium alloys and titanium alloys and their strain-life behaviour across low-cycle, medium-cycle and high-cycle fatigue range were analyzed. Substantial differences were found to exist both among fatigue parameters and among (delta epsilon)/2 - 2Nf relationships of materials belonging to these main metallic materials groups. This turns out to be in contrast with the fact that most of the existing methods for the estimation of strain-life fatigue parameters from monotonic properties show rather limited regard as to which group material in question belongs to. From results of the analysis it can be concluded that in estimation of strain-life fatigue parameters differential approach might be desirable, i.e. that separate expressions should be developed for every material group. It is expected that such an approach and resulting expressions could result in more accurate estimations of fatigue parameters and hence, more accurate estimations of time to crack initiation.