Submarine pressure hulls,fire-tube boilers,vacuum tanks,oil well casings,submersibles,underground pipelines,tunnels,rocket motor casing,etc.,are some of the examples of thin cylindrical shell structures which collapse...Submarine pressure hulls,fire-tube boilers,vacuum tanks,oil well casings,submersibles,underground pipelines,tunnels,rocket motor casing,etc.,are some of the examples of thin cylindrical shell structures which collapse due to buckling under uniform pressure.To enhance the buckling strength of bare cylin-drical shells,one of the best solutions is to stiffen them with ring stiffeners.In this work in order to predict the shell instability failure mode(SIFM)and general instability failure mode(GIFM)FE models are generated and analysed using buckling analysis of general-purpose FE software ANSYS.The numeri-cal results obtained using FE analysis are compared with published analytical and experimental results.Hence in the present study effort s are taken to develop FE models to predict global and shell instability failure modes of externally ring stiffened cylindrical shells by using linear FE analysis.It is proposed to use full/half bare cylindrical shell FE models(L/R ratio upto 200)to determine SIFM and FE models with shell281-Beam189(for stiffeners)can be used to determine GIFM.The developed FE models are vali-dated by comparing numerical results with experimental results published by Seleim and Roorda[25].By using both proposed FE models it is possible to predict the failure modes namely SIFM and GIFM,comparing their values of critical buckling pressures.The lower pressure value can indicate the possible failure mode.展开更多
Thin cylindrical shell structures have wide variety of applications due to their favorable stiffness-to-mass ratio and under axial compressive loading,these shell structures fail by their buckling instability.Hence,th...Thin cylindrical shell structures have wide variety of applications due to their favorable stiffness-to-mass ratio and under axial compressive loading,these shell structures fail by their buckling instability.Hence,their load carrying capacity is decided by its buckling strength which in turn predominantly depends on the geometrical imperfections present on the shell structure.The main aim of the present study is to determine the more influential geometrical parameter out of two geometrical imperfection parameters namely,“the extent of imperfection present over a surface area”and its“amplitude”.To account for these geometrical parameters simultaneously,the imperfection pattern is assumed as a dent having the shape of extent of surface area as a nearly square.The side length of extent of surface area can be considered as proportional to extent of imperfection present over an area and the dent depth can be considered as proportional to amplitude of imperfections.For the present numerical study,FE models of thin short carbon steel perfect cylindrical shells with different sizes of dent are generated at 1/3rd and half the height of cylindrical shells and analyzed using ANSYS nonlinear FE buckling analysis.展开更多
文摘Submarine pressure hulls,fire-tube boilers,vacuum tanks,oil well casings,submersibles,underground pipelines,tunnels,rocket motor casing,etc.,are some of the examples of thin cylindrical shell structures which collapse due to buckling under uniform pressure.To enhance the buckling strength of bare cylin-drical shells,one of the best solutions is to stiffen them with ring stiffeners.In this work in order to predict the shell instability failure mode(SIFM)and general instability failure mode(GIFM)FE models are generated and analysed using buckling analysis of general-purpose FE software ANSYS.The numeri-cal results obtained using FE analysis are compared with published analytical and experimental results.Hence in the present study effort s are taken to develop FE models to predict global and shell instability failure modes of externally ring stiffened cylindrical shells by using linear FE analysis.It is proposed to use full/half bare cylindrical shell FE models(L/R ratio upto 200)to determine SIFM and FE models with shell281-Beam189(for stiffeners)can be used to determine GIFM.The developed FE models are vali-dated by comparing numerical results with experimental results published by Seleim and Roorda[25].By using both proposed FE models it is possible to predict the failure modes namely SIFM and GIFM,comparing their values of critical buckling pressures.The lower pressure value can indicate the possible failure mode.
文摘Thin cylindrical shell structures have wide variety of applications due to their favorable stiffness-to-mass ratio and under axial compressive loading,these shell structures fail by their buckling instability.Hence,their load carrying capacity is decided by its buckling strength which in turn predominantly depends on the geometrical imperfections present on the shell structure.The main aim of the present study is to determine the more influential geometrical parameter out of two geometrical imperfection parameters namely,“the extent of imperfection present over a surface area”and its“amplitude”.To account for these geometrical parameters simultaneously,the imperfection pattern is assumed as a dent having the shape of extent of surface area as a nearly square.The side length of extent of surface area can be considered as proportional to extent of imperfection present over an area and the dent depth can be considered as proportional to amplitude of imperfections.For the present numerical study,FE models of thin short carbon steel perfect cylindrical shells with different sizes of dent are generated at 1/3rd and half the height of cylindrical shells and analyzed using ANSYS nonlinear FE buckling analysis.
