Residual Strength Analysis Of The Damaged Cylindrical Shell

The cylindrical shell will have geometrical imperfection when it was building, then the geometrical imperfection will reduce the critical pressure of submersible pressure cylindrical shell. And the cylindrical shell will make permanent deformation when the dive device happen accidents, such as hitting with other ships or rock. So there are big pits on the pressure hull, it will very reduce the depth of the submersible can descend. The catastrophic accident will happen when the dive device descend too depth, so it is important that analysis of the damaged cylindrical shell's residual strength.The buckling of the structure of the submarine is different when the geometrical imperfection is different. When the geometrical imperfection is small, the pressure hull will all buckling as wave form, when the geometrical imperfection is big. the pressure hull will local buckling. So the analysis method of the damaged cylindrical shell's residual strength is different.This paper study some methods of the buckling of the pressure cylindrical shell, sum up the advantageous and disadvantageous of the methods existed. Such as the submersible design think the nonlinear of geometry and physics is independent, but they are influence with each other. And they didn't study the damaged cylindrical shell's residual strength when the geometrical imperfection is big.Theoretical analysis of the ring-stiffened cylindrical shell geometric nonlinear buckling, this paper assumes that the pressure hulls will buckling as wave form when the geometrical imperfection is small. After study by energy method, we get the geometric nonlinear theoretical method of cylindrical shell. And the geometrical imperfection make the additional stress, so the physical nonlinear correction formula was improved by considering the additional stress.This paper checks the theoretical method by the method of experiment and FEM. We prove the theoretical method is right by experiment rusults,also prove the FEM method is right by comparing the experimental results and FEM results. Then the FEM method checke the theoretical method, study the scope of the theoretical method can be used.Analysis the residual strength of cylindrical shell be damaged seriously by FEM. Studying the influence of pit's length and depth to the residual strength of cylindrical shell, we gain the correction formula of the residual strength of cylindrical shell. Then this paper confirm the influence of the cylindrical shell's parameter u with the correction formula. Finally, gain a curve map.