Studies On Deep-sea Pressure Structural Type And Stability

Cylindrical and spherical pressure hull are the most important deep-sea pressure hull structures. The requirements for strength and stability of pressure hull structure become higher with the working depth increasing. The main ways to improve the strength and stability of deep-sea pressure hull structure are the reasonable use of different strength grades of high strength steel or high specific strength titanium alloy and the choice of reasonable pressure structural style.With the increase of material yield strength, sensitivity of structure to the initial deflection increase. So it is very necessary to research the influence of initial deflection to the strength and stability of pressure hull with high strength steel.According to its characteristic, structural style and enhance methods of deep-sea pressure cylindrical hull should be studied. The optimization design of the pressure hull parameters should be studied on the premise of ensuring the safety and reliability of pressure hull. It is very important to reduce the weight of pressure cylindrical hull, enhance the design quality and reasonableness of the structure of the pressure hull.The research work and achievements of this thesis is mainly listed as follows:(1) A finite element modeling method about the stability of pressure hull with initial deflection has been presented in this paper, the results of numerical simulation and model test is consistent. Based on the results of series calculations, the range of influence of the amplitude of initial deflection to the elastic-plastic buckling critical pressure of the shell between ribs was given. Appropriately extend the amplitude of the initial deflection, the effect on buckling critical pressure of pressure cylindrical shell is small, such as from 0.2t to 0.25t, the elastic-plastic buckling critical pressure of the shell between ribs drop less than 5%.(2) To compare and optimize the structure types of deep-sea pressure hull adopted high strength steel. The results show that, the ratio of volume to weight of T-rib cylindrical shell is inversely proportional to material yield strength and proportional to the maximum working pressure almost nothing to do with the length ratio radius; to set intermediate rib can improve stability effect of high strength steel pressure cylindrical shell evidently, when the value is small, there is a critical stiffness of intermediate rib, when the value is larger, does not exist critical stiffness of intermediate rib.(3) Experimental research on mechanical properties of polyurethane material and composite sandwich structure material has been carried out in the country for the first time. By contrast and analysis of sample test and numerical simulation, the mechanical parameters of the new material were given. This lay the foundation of the new materials for application in related fields.(4) For the first time in the domestic contrastive study of structure properties of steel-Polyurethane Sandwich deep sea pressure was carried out. It discusses the influence of changes of core thickness, ribs distance and rib sizes to the nonlinear stability of composite sandwich structure pressure cylindrical hull. Comparing with the traditional pressure structure, it does not reduce the strength of the original structure, and steel-polyurethane composite sandwich structure can improve the nonlinear instability critical pressure and resistance to local shocks of pressure cylindrical shell significantly.