Mechanical Design of external pressure vessel to an AUV
Artur Siqueira Nóbrega de Freitas1; Ettore A de Barros1
1 Escola Politécnica da USP
doi:10.20906/CPS/COB-2015-0361
Resumo
The Autonomous Underwater Vehicles (AUV), as well the Remotely Operated Vehicles (ROV), are unmanned technologies used in oceanographic investigations, offshore oil extraction, military applications, among others. Differently from AUVs, ROVs uses a physical connection with the surface for energy supply e data traffic. The AUVs use batteries and embedded data acquisition systems. These technologies have progressed, supported by studies in the areas of robotics, embedded systems, naval engineering, etc. This work presents a methodology for external pressure vessel design, responsible for contain and keep the internal components of the vehicle, such as on-board electronics and sensors, isolated from contact with water, creating a pressure differential between the inner and external regions. The vessel is subject to an external pressure relative to the depth of the operation, and the pressure increases in one atmosphere every ten meters, approximately. This type of pressure causes compression effects that lead to structural instability of the vessel, phenomenon dependent on the type of material and geometry, known as buckling. Buckling can make the pressure vessel structure to lose its stiffness before reaching the yield point. Therefore, when submitted to buckling the structure, or part of it, may lose its capacity to withstand the external load. In this context, the analysis of elastic instability and alternative constructive solutions are discussed. The methodology is based primarily on material selection. Some comparison criteria are presented and, taking into account the operational conditions, the most suitable material is chosen. A discussion on the comparison between composite and metallic materials is presented as an alternative. Structural design formulas for buckling prevention of conventional shapes (cylindrical, conical and spherical) are presented and analyzed. Assembling those shapes into a single body is investigated as well. Alternative solutions, such as reinforcement rings and
Palavras-chave: AUV; external pressure; vessel; buckling