A study on the pressure vessel design, structural analysis and pressure test of a 6,000 m depth-rated unmanned underwater vehicle

Abstract

KORDI-KRISO (Korea Ocean Research & Development Institute -Korea Research Institute of Ships & Ocean Engineering) is currently conducting the development of an unmanned underwater vehicle (UUV) for 6,000 m deep-sea exploration, which will be completed in 2006. Several pressure vessels will be mounted on the UUV frame for loading electric and electronic equipment. The pressure vessels are constructed with titanium alloy Ti-6Al-4V for two main cylindrical canisters and with aluminum alloy A16061-T6 for several hemispherical housings of electric motor drivers, respectively. This paper presents the design process of the pressure vessels and experimental results acquired by high-pressure tests, which were conducted with the cooperation between KORDI-KRISO and JAMSTEC (Japan Agency for Marine-Earth Science and Technology). The pressure vessels were designed based on the buckling analysis as well as structural yielding analysis, and checked the safety by the FEA (Finite Element Analysis) and analytical (empirical) formula. Moreover, by structural reliability analysis, the cylindrical part and the end-plates of the main pressure vessels made of Ti-6Al-4V were designed with a safety rate of 99.98% under circumstance of 75MPa which is the same pressure and safety rate 1.25 as with the operating depth of the pressure vessel. The pressure housings made of A16061-T6 also were designed with the same safety factor. Pressure test was performed with the large high-pressure environment simulation unit of JAMSTEC. The pressure vessels made of the titanium alloy and the aluminum alloy were safe even when they were under pressure of 75.46MPa. Test results show that there are less than 5% difference between the FEA and the high-pressure test. Copyright ？ 2005 by The International Society of Offshore and Polar Engineers.