Buckling Analysis of an AUV Pressure Vessel with Sliding Stiffeners

Abstract

The structure of an autonomous underwater vehicle (AUV), usually composed of a cylindrical shell, may be exposed to high hydrostatic pressures where buckling collapse occurs before yield stress failure. In conventional submarines, welded stiffeners increase the buckling resistance, however, in small AUVs, they reduce the inner space and cause residual stresses. This work presents an innovative concept for the structural design of an AUV, proposing the use of sliding stiffeners that are part of the structure used to accommodate the electronics inside it. Since the sliding stiffeners are not welded to the shell, there are no residual stresses due to welding, the AUV fabrication process is simplified, enabling a reduction of the manufacturing cost, and the inner space is available to accommodate the equipment needed for the AUV mission. Moreover, they provide a higher buckling resistance when compared to that of an unstiffened cylindrical shell. A comparative analysis of the critical buckling loads for different shell designs was carried out considering the following: (i) the unstiffened shell, (ii) the shell with ring stiffeners, and (iii) the shell with sliding stiffeners. Results evidenced that major advantages were obtained by using the latter alternative against buckling.

Exploring Autonomous and Remotely Operated Vehicles in Offshore Structure Inspections

“…Automated underwater vehicles (AUVs) have become essential tools for inspecting offshore structures due to their ability to carry a large amount of equipment at a relatively low operational cost [77,78]. These vehicles are widely used for subsea tasks such as mapping the seabed, inspecting underwater equipment and pipelines, and conducting environmental surveys [79].…”

“…The design and instrumentation of AUVs play a crucial role in their effectiveness for offshore structure inspection. The structure of an AUV, typically composed of a cylindrical shell, needs to be analyzed for buckling resistance under high hydrostatic pressures [78]. Sliding stiffeners have been proposed as an alternative to welded stiffeners to increase buckling resistance while maintaining the inner space for equipment [78].…”

“…The structure of an AUV, typically composed of a cylindrical shell, needs to be analyzed for buckling resistance under high hydrostatic pressures [78]. Sliding stiffeners have been proposed as an alternative to welded stiffeners to increase buckling resistance while maintaining the inner space for equipment [78]. The use of vectored thrusters based on parallel manipulators has been investigated to improve the control and manoeuvrability of AUVs [86].…”

Evolution of Standardized Specifications on Materials, Manufacturing and In-Service Inspection of Nuclear Reactor Vessels

“…The imperfections found in structures may be classified into global or local types: the first ones are related to deviations of the "perfect structure" that extend to a large part of the component (e.g., out-of-roundness of the cross-sections or thickness variations), whereas the latter ones are related to those deviations that are restricted to a small part of the component (e.g., small dimples or small indentations on the shell surface, welding defects, small corroded areas, etc.) [43]. Heat treatment technology (normalizing and tempering) for large forgings is based on the experimental investigations and experiences of actual operation in addition to heat treatment theory.…”

Design by analysis of deep-sea type III pressure vessel

“…They observed no influence of the winding pattern on the buckling behaviour. The use of sliding stiffeners, on the other hand, can increase the buckling resistance up to 41% when compared with a conventional unstiffened cylinder made of aluminium [19]. Cai et al [20] employed the reliability-based load and resistance factor design (LRFD) method to design a type III pressure vessel for subsea applications subjected to an external pressure of 120 bar.…”