Numéro : 2519 - Year : 2008
Fatigue behaviour assessment of naval type welded joints
Carole ERNY, DCNS – DCSE/AS – Lorient (France) & Laboratoire Brestois de Mécanique et des Systèmes – EA ENSIETA/ Université de Brest/ ENIB– Brest (France)
David THEVENET, Laboratoire Brestois de Mécanique et des Systèmes – EA ENSIETA/ Université de Brest/ ENIB– Brest (France)
Jean-Yves COGNARD, Laboratoire Brestois de Mécanique et des Systèmes – EA ENSIETA/ Université de Brest/ ENIB– Brest (France)
Welding is one of the most commonly used processes to build naval structures. However, the geometry, induced by welded joints, generates local stress concentration. Moreover, all these structures undergo some variable and complex cyclic loadings. Accordingly, welded joints could be a critic area regarding fatigue damage. During the first stage of this ongoing project, a strategy has been developed to predict fatigue life of basic welded specimens such as butt-welded joints. This method can be split into two stages: the structure shakedown study and the fatigue crack initiation study. The time needed to initiate a fatigue crack can be determined by using a two scale damage model. A good correlation between numerical and experimental life span has been obtained. Therefore, based on results and methodologies developed in this previous work, we focus on more complex assemblies. This work deals with the fatigue behaviour of welded structures representative of naval structures. Two different steels are commonly used in naval construction (S355NL and DH36) and so we need to characterize their mechanical behaviour. Several naval welded structures have been designed (cruciform joints and representative structures of naval applications) in order to estimate their fatigue life.
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