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Comparison of hydrostatic pressure test and finite element analysis results of cylindrical pressure vessel with various thicknesses

The collapse behavior of offshore apparatus under external pressure is a primary concern for design criteria of structural integrity. Finite element analysis of the collapse behavior for various thick and thin-walled pressure vessels under external hydrostatic pressure were performed. The cylinder and both ends are connected by welding or bolting, and the ultimate collapse points are usually near the connected part while initial plastic deformation occurs in the form of buckling in the cylindrical part. Therefore, in order to evaluate the structural safety of the pressure vessel, it is necessary to consider the failure of the connection part, together with the cylindrical part in the middle and both ends, where the initial large deflection occurs. Local structural analysis for the pressure vessel considering the bolted part was carried out as well as global buckling analysis. That is, aluminium alloy and stainless steel pressure vessel models were designed for operating under high pressure equivalent to the water depth up to 2000m and 1000m, respectively. Pressure vessel design procedure was performed by using empirical formulae and eigenvalue analysis by FEM code. The results were verified and investigated by pressure tests in the hyperbaric chamber of KRISO. It was found that all the estimated results by the empirical formula and FEA are overestimated when the results are compared to the pressure test results in the pressure chamber.