Preliminary Research On Strength And Stability Of A Saddle Pressure Bulkhead

Stern-pressure bulkhead is a significant component of a submarine. Plane bulkhead and spherical bulkhead are usually used in submarine in service. But in practice, these two forms of bulkhead have some shortcomings. With the development of submarine to more deep sea and high-speed, and the enhancement of submarine's attack capability, the requirement for the carrying capacity of the pressure bulkhead is raised. Thus, the design of new-style structure of pressure bulkhead, which has better strength, stability and ultimate carrying capability against impact and lower sensitivity to deflection, is very important to the safety and reliability of submarine structures.Recently proposed saddle-shaped bulkhead is a new kind of pressure bulkhead, which consists of spherical shell, reversed spherical shell and a strength frame between the two parts of shells to improve its stability. Research on this type structure is rather limited. However the understanding of the strength and stability characteristics of the new-style bulkhead is very important for the design of submarine pressure bulkheads, therefore the strength and stability of the saddle-shaped bulkhead is studied in the thesis.In this thesis, finite element software is employed to analyze the characteristics of the saddle-shaped bulkhead's strength and stability. After the connection position and chamfer angle between the shell and the strength frame are chosen , the influence of the major structural parameters including the thickness of the shells,the radius of the reversed spherical shell,the height from the frame to the bottom of the bulkhead,the sectional parameters of the strength frame on the strength of the saddle-shaped bulkhead is discussed in detail. The stress concentration at the connection between the shells and the strength frame is also investigated and the stress concentration coefficient and the influence region are analyzed. The influence of tail shaft opening on the strength of the bulkhead is also discussed. For the stability of the bulkhead structure, nonlinear buckling analysis is carried out to obtain the extreme load of the structure, which is very significant. Similar to the analysis of strength, the influence of the major structural parameters on the stability of the saddle-shaped bulkhead is discussed in detail as well. To increase the ultimate load of the structure, the method of local thickening the spherical shell is proposed, and the region which is thickened can refer to the strength analysis.In the thesis, many chars and graphs are given based on a lot of numerical analyses and some useful conclusions have been drawn,which are helpful to understand the mechanical performance of such a special bulkhead structure and certainly useful for the design of the saddle-shaped bulkhead.