Study On Mechanical Properties And Experimental Study Of Deep-sea Pressure Spherical Hull Viewport

Pressure hull is an important structure of deep-sea manned submersible.Various openings are arranged on the pressure hull,such as manhole for access,viewports for external observation and through holes for parts and pipe fittings.Openings will weaken the mechanical properties of spherical hulls,so the design of the opening structure is the key to the design of pressure spherical hulls.As a window for drivers to observe the surrounding environment,the viewport is subject to complex stress,and the material properties of the viewport are quite different from those of the pressure hull.Under the action of deep-sea pressure,the viewport will produce extrusion deformation,which may lead to the extrusion of the viewport from the window seat and thus cause the leakage.In order to ensure the safety of personnel and equipment and the normal operation of submersible in deep sea,it is very important to study the openings on pressure hull,including the manhole and the viewport.The main contents are as follows:(1)Firstly,the structural stress of the pressure hull with the conical frustum viewport was studied by two theoretical formulae,and the applicability of the two formulae under different thickness radius ratio was discussed.When the spherical shell is medium thick,the results of the two theoretical formulas are close.The effect of structural parameters of window seat on stress concentration coefficient was studied.The changes of parameters a,b and c have less effect on k_ρand greater effect on k_θ,while parameter f has little effect on the two kinds of stress concentration coefficient.The stress of viewport was analyzed by theoretical and numerical methods.The variation trend of the axial stress obtained by two methods is approximately the same,and the numerical solution is slightly larger than the theoretical solution.The stress concentration is easy to occur at the sharp corner of the small diameter end of the viewport,and the strain at the small diameter end is large,which may cause the inconsistency between the deformation of the viewport and the window seat.In order to explore the compatibility of the deformation between the viewport and the window seat,the stress and deformation at the interface were studied by using the structural parameters of the viewport.(2)The strength of pressure hulls with different viewports was studied by theoretical and numerical methods.The results showed that the numerical analysis results were in good agreement with the theoretical analysis results.The maximum stress of pressure hull with a plane disk viewport is quite different from that of a perfect spherical hull.The maximum stresses of pressure hulls with a spherical sector viewport or a conical frustum viewport are basically the same as that of a perfect spherical hull.The cone-shaped window seat compensates for the weakening of the strength of spherical hull by opening.Secondly,the proportional resin model was manufactured for experimental verification.The instability forms obtained by numerical method and experimental method were well consistent.Therefore,numerical analysis considering equivalent defects could well predict the failure forms and failure loads of spherical pressure hulls.(3)The effect of multiple openings on the mechanical properties of spherical pressure hulls was studied.The strength and stability of the pressure hull with a manhole were numerically analyzed.The results were verified by hydraulic test.The results showed that the experimental results are in good agreement with the numerical analysis results considering real defects,and that the rationality of the numerical analysis is verified.The mechanical properties of a pressure hull with a manhole and three viewports were studied to verify that it meets the strength requirements.The critical load of multi-hole pressure hull is2%higher than that of single viewport pressure hull,1.2%higher than that of perfect spherical hull,and 1.1%lower than that of manhole pressure hull.It shows that the reinforced structure of manhole and the window seat make up for the weakening of mechanical properties of pressure hull caused by opening.Structural strengthening has played a strengthening role.