Research on Fabrication Procedure of Spherical Pressure Hull Made from Titanium Alloy for Deep Submergence Research Vehicle (2 nd Report)

Abstract

Following “Shinkai 2000”, as Japanese deep research project, a 6000 m class deep submergence research vehicle is under planning. For the research vehicle of this class, from the maneuverability and operationability, of utmost importance is the reduction of weight. As for a pressure hull, which houses crew members, the authors have carried out a series of research for the application of titanium alloy (Ti-6 Al-4 V ELI) considering the strength-weight ratio, and anti-corrosion capability against sea water. In the 1 st report, the authors have made a full scale model of the pressure hull of Ti-6 Al-4 V ELI for the 6000 m class submersible to establish the manufacturing procedure. In this report, by disassembling the model, the authors have investigated the material characteristics for the application of a deep submergence research vehicle. The research covered the fields of mechanical properties, fracture toughness, fatigue strength, stress corrosion cracking, hardness distribution, micro-structure, and residual stress. As a result, 6 A1-4 V titanium alloy was confirmed to be one of the most effective material for the pressure hull of a deep submergence research vehicle.