Article : [ART160]
Info : REPONSE 23, le 04/02/2002.
Titre : Fatigue life assessment of nodular cast iron containing casting defects.
Cité dans : [DIV313] Recherche sur l'auteur Narayanaswani RANGANATHAN, février 2002.Auteur : Nadot, Y. (ENSMA, Futuroscope, Fr)
Source : Fatigue and Fracture of Engineering Materials and Structures v 22 n 4 1999.p 289-300
CODEN : FFESEY
ISSN : 8756-758X
Année : 1999
Document_Type : Journal
Treatment_Code : Theoretical; Experimental
Language : English
The fatigue behaviour of a nodular cast iron containing casting defects has been investigated in the
high-cycle fatigue regime.In this paper, we propose a fatigue life assessment model for flawed materials
based on a fracture mechanics approach which takes into account the position and size of the defect, short
crack behaviour and the notch effect introduced by the defect.The fatigue behaviour of smooth samples, and
long and short crack behaviour have been experimentally determined in order to identify the relevant
mechanical parameters; these being introduced into the model.An experimental study has been made both in
air and in vacuum in order to account for the position of the defect, noting that internal defects are supposed
to be under vacuum conditions. Experimental results, which are based on a two-crack front-marking
technique specially developed for this study, show that the propagation of natural cracks is controlled by the
effective stress intensity factor in air as well as in vacuum.The K calculation for a short crack in the stress
field of a notch is analyzed using numerical elastic-plastic results.Comparison between experimental results
and the computation of fatigue life for fatigue lives less than 106 cycles shows that the fatigue behaviour of
nodular cast iron is controlled by a propagation process.The model proposed is thus relevant for fatigue lives
less than 106 cycles SO that the defect can be considered as a crack and the initiation stage neglected.Closer
to the fatigue limit, this study shows that the initiation stage should be considered in the assessment of fatigue
life of nodular cast iron, because a single macroscopic propagation assessment is not enough to describe the
whole fatigue life.The defect cannot be considered as a pre-existent crack in the high-cycle fatigue range (
greater than 106 cycles), and the initiation stage that contains microcrack propagation around the defect
should be evaluated when assessing the high-cycle fatigue life of nodular cast iron.(Author abstract) 25 Refs.
Accession_Number : 1999(31):1849 COMPENDEX
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