Comparison of Design Criteria for Externally Pressurized Vessels

The design of an underwater chemical species concentration probe using optical diagnostics for depths of up to 1000m is presented. An initial investigation into the most appropriate spectroscopic techniques and the required geometries is followed by an investigation into the application of current externally loaded pressure vessel theory and a comparison with a finite element model. The probe geometry can be approximated as a cylindrical object with a center tube which is open to the ambient. The ultimate goal being to propose a housing which will be able to operate safely and reliably. The finite element program ABAQUS is used to analyze the different configurations using a static analysis across the different models as a comparison. As most externally loaded pressure vessels initially fail in an elastic buckling mode it is also necessary to investigate the modes of failure and to improve the design. The buckling modes are analyzed by means of an eigenvalue investigation on each model, which are then imposed on a perfect model as an imperfection to induce a failure. A static analysis is used to simulate the loading conditions experienced in operation and the external pressure and arc length are solved simultaneously to find a failure point.© 2009 ASME