Strength And Deformation Analysis Of The Ring-stiffened Circular Toroidal Shells

Underwater vehicles can play an important role in the areas such as deep-sea exploration, underwater experimental study, underwater operation and control, underwater comprehensive supply, etc. The hull of an underwater vehicle is the all-important and decisive technology that relates to the capability to resist deep-sea water pressure and the overall performance. In view of the disadvantages of the cylindrical pressure hulls and the widespread application of the circular toroidal shell structures in engineering, it is of great engineering significance to research on the structural characteristics of the circular toroidal shells that act as major structures.Used in underwater engineering, a series of annular ribs need to be set to enhance the stability of the circular toroidal shell structures. While advantageous to the stability, the ribs may be disadvantageous to the strength of the circular toroidal shell structures sometimes. Therefore the strength of the rib-stiffened circular toroidal shell structures is a problem urgently waiting to be solved. But at present most of researchers are focusing on the circular toroidal shells without ribs, while few of them are turning to the rib-stiffened circular toroidal shells. In this thesis, contrastive analysis of the structural strength performance between the rib-stiffened circular toroidal shells and the rib-stiffened circular cylindrical shells are carried out and and the variation attribute of the structural characteristics of the rib-stiffened circular toroidal shells with the structural parameters is analyzed by theoretical and numerical methods respectively. The research contents of this thesis are as following:(1) The deformation and the stress characteristics of the circular toroidal shells are analyzed by the theory of elastic thin shells. The variation law of the principal stress with the location parametersφand the relative bending radius R a is studied, and thus the difficulties in solving theoretically and the structural characteristic are revealed that moments exist even though the circular toroidal shells are at membrane stress condition.(2) In accordance with the characteristic that the load and the deformation of the rib-stiffened circular toroidal shells is symmetrical in the cross-section where rib exists under hydrostatic pressure, a simplified mechanical model is firstly developed in this thesis, which considers the influence of ribs on the bending of the shells. In this model, the deformation of the rib-stiffened circular toroidal shells can be simplified to the complex bending of the elastic foundation curved beams, both ends of which are clamped rigidly on the elastic supports.(3) Based on the theory of elastic curved beams and thin shells, the theoretical expression of the displacement and the stress in the key sections of the rib-stiffened circular toroidal shells is firstly deduced, applied the principle of simplification and equivalent. Consequently, the analytical and calculation method on the strength and the deformation of the rib-stiffened circular toroidal shells is presented here.(4) The finite element method (FEM) is used to confirm the theoretical solution of the rib-stiffened circular toroidal shells proposed in this thesis. Comparative results of the two methods show good agreement and meet the accuracy requirement in engineering, which demonstrate the correctness of the theoretical solution and the rationality of the theoretical method.(5) Contrastive analysis of the characteristic parameters of the structural strength is carried out for the first time between the rib-stiffened circular toroidal shells and its equivalent rib-stiffened circular cylindrical shells using the theoretical solution proposed in this thesis and the variation attribute of the stress at the typical locations in the rib-stiffened circular toroidal shells with the structural parameters is investigated.