Study On Confined Buckling Of Thin Cylindrical Shells

Confined buckling is the buckling that the buckling configuration of structures can not develop freely due to constraints. Compared with the buckling of structures not confined, the characteristic of the structure will be changed during the buckling, and the classical bifurcation curve will be modified. The work to study this kind of problem become very complicated as a result of the existence of constraints which brings in nonlinear problems, such as contact, non-conservation and friction etc.Based upon the progress on confined buckling of the cylindrical shell is summarized, the control equation for the buckling of the cylindrical liner under uniform external pressure was derived using the principle of minimum potential energy. The critical buckling problem of the cylindrical liner was solved using Galerkin method according to the corresponding boundary conditions and constraints of the liner. The shortened scaling factor of the wavelength was introduced, and the impact of the contact between the cylindrical liner and the wall of the outer equipment on the critical buckling pressure of the cylindrical liner was studied. The results show that, if the contact between the cylindrical liner and the wall of the outer equipment is not considered and the displacement is confined in the cavity of the outer equipment, the critical buckling pressure of the confined cylindrical liner increased about by 36% than that of the non-confined cylindrical liner in the range of the model size the paper selected. The circumferential buckling wavelength of the cylindrical liner is shorter than that of the non-confined cylindrical shell when the contact between the cylindrical liner and the wall of the outer equipment is considered. And the critical buckling pressure of the liner is over three times than that of the non-confined cylindrical liner when the circumferential buckling wavelength of the cylindrical liner is reduced to half of the non-confined cylindrical liner.Three-dimensional finite element model of the cylindrical shell with the cavity was established, and the buckling of the cylindrical shell confined by the cavity is studied using ANSYS. Results show that the critical buckling pressure of the cylindrical shell increased much as a result of constraints, and the degree of increasing is relation to the gap existed between the cylindrical shell and the cavity. The bigger the size of the gap, the lower the critical buckling pressure of the cylindrical shell.The buckling of thin cylindrical shell clamed hoops was studied using nonlinear buckling analysis technology. The effect of the position of hoops, the number and the width of the hoop, and the distance between the two hoops to the critical pressure of the cylindrical shell were discussed. Results show that the critical buckling pressure of the cylindrical shell greatly influenced by the position of hoops, and it gets highest when the hoop located in the middle of the cylindrical shell. With the increase of number and width of the hoop, the critical pressure of cylindrical shell increases. In addition, the hoop has little influence on the critical pressure of the cylindrical shell when the ratio of the distance between two hoops for the outer diameter of the cylindrical is 20.