evaluation of buckling and post buckling of variable thickness shell subjected to external hydrostatic pressure

Buckling and post buckling of cylindrical shells under hydrostatic pressure is regarded as important issue in structure of submarines. these cylindrical shells have variable thickness due to construction process which effected by pressure of buckling and its destruction. in this paper, effects of changing thickness on buckling and destruction pressure under external hydrostatic pressure of a shell are studied. results of buckling pressure of cylindrical shell have been obtained with theoretical relations and finite element method. then, using machining process a sample of cylindrical shell with variable thickness has been produced. buckling pressure and post buckling of the constructed sample have been obtained with the reservoir under closed-ended hydrostatic pressure. changes of the test sample size have been considered with closed-ended testing apparatuses which are used for new evaluation of buckling. in this research, results of the pressure have been obtained in terms of the volume change. at the end, results of the finite element method have been compared with results of the analytical solutions and experimental data. results show that the shell with variable thickness has buckling pressure close to shell bucking pressure with mean thickness.