A study of diving depth on deep-diving submersible vehicles

Abstract

Among the many deepwater activities in which deep-diving submarines have been used are marine research, deep ocean mining and submarine rescues. To resist high hydrostatic pressure and obtain more inner space, a deep-diving submersible pressure hull is normally constructed from high strength steel and a simple geometrical configuration, e.g. spherical, elliptical and cylindrical shells. The material properties, weight/volume ratio and aspect ratio profoundly influence the diving depth of pressure hulls. The accurate calculation of strength is a priority in developing deep-diving submarines. In the present work, we investigate the diving depths of spherical and elliptical shells. Also considered are the geometrical non-linear and elastoplastic material behaviour of high-yield steels, as well as the effect of weight/volume ratios and aspect ratios on the geometrical configuration. High-yield steels, i.e. HY80, HY100 and HY140, are adopted here. In addition, the finite element procedure based on Hibbitt and Karlsson's methodology is used to analyse the diving depth of the shells. Experimental results indicate that for a spherical shell with aspect ratio a/ b=1 and weight/volume ratio W/ V=0.685 ton/m 3, HY140 steel has the greatest yielding diving depth, i.e. 5238.6 m and ultimate diving depth, i.e. 5957.9 m. Moreover, the difference between diving depth at yielding strength and diving depth at ultimate strength is 719.3 m, i.e. lower than the difference of 1020.2 m for HY80 and 840.6 m for HY100. Although a pressure hull of HY140 steel has a deeper diving depth than HY80 and HY100 steels, the difference between yielding and ultimate diving depth is smaller than the others, because the ability to sustain plastic deformation in HY140 is lower than in HY100 and HY80 steels. According to our results, a deep diving submersible pressure hull having a larger aspect ratio, has a larger diving depth. In addition, a higher weight/volume ratio implies a larger diving depth. Moreover, a higher yielding/ultimate strength implies a deeper diving depth.