Submarine pressure hull collapse: A correlation between numerical and experimental analyses

A ring stiffened cylinder representing, in scale, the hull of a submarine, has been studied by numerical and experimental approaches. The laboratory tests were carried out at Defence Research Agency in Dunfermline, Scotland. The structure, the imperfections of which were caused by the manufacturing process, was subjected to an increasing external pressure up to collapse. A numerical, nonlinear analysis was performed by a finite elements program, in order to simulate the behavior experimentally observed on the structure. Initially, parametric investigations using different models and different elements of the code library were carried out. On the simplified numerical models the suitability of the chosen elements and the influence of the mesh refinements were analyzed in order to individuate the most suitable meshes. A series of finite elements models have then been investigated, at first, by applying separately the different kinds of imperfections measured on the specimen and then considering all the defects simultaneously. The correlation between numerical and experimental results has been performed in terms of collapse pressure, failure mechanism and strain distribution. A good agreement has been achieved only when a very refined mesh was adopted.