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Influence du chargement sur la propagation en fatigue de fissures courtes dans un acier de construction navale

Abstract : Our study related to a naval structural steel (type S355NL) employed in ship structures. If the behavior of the long cracks is well known, that of short cracks is controlled little. These two types of cracks actually present only few common points and the step to be adopted of the study of these short cracks required a particular reflexion. It is in particular significant to note that the short cracks propagation rate is influenced considerably by the microstructural components of the material (inclusions, grain boundary...). Tests with constant loading amplitude first of all were undertaken to characterize the short cracks behavior. The load ratios used for these fatigue tests were 0.1, 0.3, 0.5 and finally -1. Tests with variable amplitude (increasing, decreasing and resulting from a loading spectrum) were also carried out. This work gave many experimental results concerning fatigue cracks propagation which they are propagative or not propagative cracks and this starting from a measurement size of 20-25 µm. The results obtained were systematically compared with the long cracks propagation curves (da/dN –∃Keff) also established for this material.
Parallel to this work, a numerical study was undertaken by using the finite elements code Abaqus\Standard. We first of all determined the load distribution and stress concentration factor KT in the initiation area for the specimens used. Then, with a view to calculating the stress intensity factor K necessary to modeling the fatigue cracks behavior, several calculations based on the concept of J integral were carried out. Those were established for various configurations of specimens and cracks (semi-elliptic, semicircular, corner, surface...) in the elastic and elastoplastic cases. Lastly, two laws were proposed to predict the propagation life of fatigue crack.
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https://tel.archives-ouvertes.fr/tel-00204096
Contributor : Aboulghit El Malki Alaoui <>
Submitted on : Friday, January 11, 2008 - 6:12:02 PM
Last modification on : Friday, December 13, 2019 - 10:42:04 AM
Long-term archiving on: : Tuesday, April 13, 2010 - 5:08:01 PM

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  • HAL Id : tel-00204096, version 1

Citation

Aboulghit El Malki Alaoui. Influence du chargement sur la propagation en fatigue de fissures courtes dans un acier de construction navale. Mécanique [physics.med-ph]. Université de Metz, 2005. Français. ⟨tel-00204096⟩

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