Numéro : 2496 - Year : 2007
Fatigue behaviour evaluation of submarine resistant structures
Manuel KÖRNER, DCNS Ingénierie Navires Armés – Lorient (France)
Aude MÉNÉGAZZI, DGA/SPN – Paris (France)
Within an R&D program financed by the naval directorate of the French defense procurement agency, DCNS developed two methods to estimate the fatigue behavior of resistant structures of submarines.
The first approach is based on damage mechanics. A cyclic elastic-plastic analysis is made with a material law which takes into account the distinction between isotropic and kinematic hardening. The results are injected in a Smith-Watson-Topper multiaxial damage model, allowing us to deduct the crack initiation life.
The second approach is based on fracture mechanics. This method considers the propagation of an elliptic or semi-elliptic crack in the heat-affected zone of a welded connection. In this respect, it is necessary to consider the residual stresses, on top of the hull stresses due to the submersion pressure. The application field of this method includes assessment of the acceptability of crack type flaws, which would be put in evidence by non-destructive testing.
Experimental results, stemming from cyclic loading applied to specimens and to a large-sized stiffened structure, allowed to verify the aptness of these two approaches.
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