Acrylic Pressure Hull Research Articles

Acrylic spherical pressure hull for Manned Submersible

Materials used for construction of ocean exploration vehicles require excellent resistance to corrosion in marine environment and higher strength to weight ratio. Acrylic is one of such material which has added benefit of having transparency to be used as material for construction of human occupied pressure hull for Manned Submersible. This paper describes approaches for the design of acrylic pressure hull for sea water depth by utilizing the empirical procedures of ASME PVHO-1. It also presents finite element analysis for the comparison with results of analytical calculations. Based on finite element analysis model, stress and deformation characteristics have been accomplished and then collapse pressure has been analyzed through non-linear buckling analysis considering imperfection during manufacturing. Finite element analysis shows that the acrylic spherical pressure hull is safe for designed sea water depth for an application of human occupied pressure rated cabin in Manned Submersible.

Spherical Acrylic Pressure Hulls With Multiple Penetrations

An experimental program has been conducted to determine the effect of multiple penetrations on the performance of spherical acrylic plastic hulls under external hydrostatic pressure. As test specimens served 15-in. OD × 14-in. ID model scale NEMO spheres. The distribution of strains and the magnitudes of short term critical pressures indicate that the structural response of acrylic spheres with multiple penetrations to external hydrostatic pressure is identical to spheres with only one penetration equipped with a metallic closure providing that the included angles of the penetrations are ≤46 deg and the edges of the penetrations are at least one penetration radius apart. Based on these findings it is feasible to incorporate three or more large penetrations into the spherical hulls of acrylic submersibles without decreasing their operational depth rating that has been based on the experimentally proven structural performance of spheres with only one penetration, or two penetrations 180 deg center to center apart.

Closure to “Discussion of ‘Spherical Acrylic Pressure Hulls With Multiple Penetrations’” (1978, ASME J. Eng. Ind., 100, pp. 271–272)

Closure to “Discussion of ‘Spherical Acrylic Pressure Hulls With Multiple Penetrations’” (1978, ASME J. Eng. Ind., 100, pp. 271–272)

Stress Analysis of a Spherical Acrylic Pressure Hull

This study was initiated to: (1) perform an analytical structural analysis on an acrylic pressure hull, (2) compare the analytical results with all available experimental results, and (3) present an operating-depth curve. The design analyzed was a pressure hull incorporating twelve spherical pentagons of acrylic plastic bonded together to form a sphere with an outside diameter of 66 in. and a wall thickness of 2.5 in. Conical steel penetrations were located at the two poles. The experimental results were obtained from strain-gage data from two independent pressure tests to 500 psi on two acrylic hulls of the same design. The analysis on the structure was performed with a finite-element computer code with particular emphasis on the acrylic-steel boundary. The boundary conditions at the acrylic-steel interface were two extreme cases: perfectly fixed and perfectly free. A time-dependent yield-failure criterion for acrylic plastic was combined with the structural analysis to provide an operating-depth curve as a function of both time and temperature. Comparison of analytical and experimental results indicated excellent agreement. At a temperature of 70 deg F and a maximum of 50 hr load duration, the acrylic hull can operate to 1000 ft with a safety factor of 1.5 based on yield and a safety factor of 2.6 based on collapse.

Closure to “Discussion of ‘Stress Analysis of a Spherical Acrylic Pressure Hull’” (1971, ASME J. Eng. Ind., 93, pp. 882–883)

Closure to “Discussion of ‘Stress Analysis of a Spherical Acrylic Pressure Hull’” (1971, ASME J. Eng. Ind., 93, pp. 882–883)

Spherical Acrylic Pressure Hulls for Undersea Exploration

The exploratory phase of the research program into the applicability of acrylic to the construction of spherical pressure hulls for undersea exploration has been completed. The findings show that acrylic pressure hulls are as reliable as hulls made from conventional materials if the viscoelastic temperature-dependent properties of the acrylic are taken into account during its design, fabrication, and operational service in the sea. The design data and information from the exploratory phase of the R & D program have been already applied to the fabrication of the NEMO Model 600 acrylic capsules with 66-in. OD × 61-in. ID for 600-ft-depth service.