Strain Measurement Validation of a Spherical Pressure Hull for Human Occupied Vehicle Using Rosette Strain Gauge

The deep-water human-occupied vehicle (HOV) MATSYA 6000 is being developed by the National Institute of Ocean Technology, Ministry of Earth Sciences, Government of India, to carry three humans up to a depth of 6000 m for deep ocean scientific exploration and research. As this underwater vehicle is man-rated, the safety and reliability of the spherical pressure hull are significant as the structure is subjected to extremely high pressures at higher depths. A spherical pressure hull of 2.1 m diameter is designed and manufactured indigenously to carry three humans up to a depth of 500 m. In this letter, triaxial strain measurements are carried out using the Rosette strain gauge at different welded locations inside the spherical pressure hull. The proposed methodology shall be used for human-rated subsea applications, which give insight and compliance in designing the human-rated systems with finite element analysis studies. The spherical pressure hull has been tested three times in the open sea at 606 m depth for a 60-min period in the Bay of Bengal. The results obtained from analysis and measurements observed from the external pressure test at open sea are comparable, and the error is less than ∼9%.