Abstract
The behavior of short cracks that depart from elastoplastic notch tips is modeled to estimate the stresses required to initiate and to propagate cracks in notched structural components, and to evaluate the size of tolerable crack-like defects under general loading conditions. This analysis can model both fatigue and environmentally assisted cracking problems; can evaluate notch sensitivity in both cases; and can as well be used to establish design or acceptance criteria for tolerable non-propagating crack-like defects in such cases. The growth of short cracks is assumed driven by the applied stresses and by the stress gradient ahead the notch tip, and supported by the material resistances to crack initiation and to long crack propagation by fatigue or EAC. In the elastoplastic case, the stress gradient ahead of the notch tip is quantified by a J-field to consider the short crack behavior. The tolerable short crack predictions made by this model are evaluated by suitable fatigue and EAC tests of notched specimens specially designed to start nonpropagating cracks from the notch tips, both under elastic and elastoplastic conditions.
Highlights
For design purposes, q-values are traditionally estimated by fitting semi-empirical models to data from fatigue tests of notched components
Q has long been associated to non-propagating short cracks that start at the notch tips but stop after growing for a small distance [2,3,4]
It allows the notch sensitivity concept to be extended to environmentally-assisted cracking (EAC) problems as well, and its predictions have been validated under liquid metal embrittlement conditions by testing notched Al samples in a Ga environment [8], as well as under hydrogen embrittlement conditions by testing similar steel samples in aqueous H2S environments [9]
Summary
Q-values are traditionally estimated by fitting semi-empirical models to data from fatigue tests of notched components. Most long-life designs just intend to maintain the service stresses at the structural component’s critical point below its fatigue limit, < SLR/ F, where F is a suitable safety factor for fatigue applications Such calculations can be quite complex (e.g. when analyzing fatigue crack initiation caused by random multiaxial non-proportional loads), their so-called safe-life philosophy is not intrinsically safe. This simple (but quite reasonable) model indicates that the studied structural component tolerates well small edge cracks up to a 30 m, since they almost do not affect its original fatigue limits The FCG behavior of microcracks with sizes a and a0 < gr is sensitive to microstructural features, but since grains (let alone dislocations) cannot be mapped in practical applications yet, their use for structural engineering purposes may be questionable
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
