Numerical Simulation And Experimental Research On The Static And Dynamic Buckling Characteristics Of Thin-Walled Stiffened Cylindrical Shell

The thin-walled stiffened cylindrical shell is an extremely important engineering structure element and it is more and more widely used in such fields as ship&ocean engineering and aerospace and its static and dynamic buckling has become the important research topic in the solid mechanics field.The static stability characteristic and dynamic buckling characteristic under the coupling loading of static and dynamic load of the thin-walled stiffened cylindrical shell are mainly studied in the thesis.For the study on the static stability of the thin-walled stiffened cylindrical shell,first,both arc length method and damping factor method are used to established the non-linear static buckling model,taking into account the initial geometrical imperfection of the structure,thereinto,imperfection distribution mode with uniform combination mode amplitudes and imperfection distribution mode with single mode are used to consider initial geometric imperfections of the structure.Then,based on the above methods and models,the effects of the shape and amplitude of imperfection on the axial compression and radial compression stability of grid stiffened cylindrical shells are systematically discussed.The numerical result shows that the sensitivity of the axial pressure buckling load of the grid stiffened cylindrical shell to the shape and amplitude of the initial geometrical imperfection of the former is smaller than that of the latter while the radial pressure buckling load of the grid stiffened cylindrical shell to the shape and amplitude of the initial geometrical imperfection of the former is greater than that of the latter.Taking the first-order eigenvalue buckling mode as the design imperfection shape is very unfavorable to the structure stability,but it is not the imperfection shape which is the most unfavorable to the structure stability;relative to the lower-order eigenvalue buckling mode,taking the higher-order eigenvalue buckling mode as the design imperfection shape is more favorable to the structure stability.Finally,the influence of the pre-added axial pressure on the radial pressure buckling characteristic based on the static stability of the coupling loading of axial and radial pressure of the grid stiffened cylindrical shell is discussed.Conclusions are as follows:with the increase of the pre-added axial pressure,the radial buckling load reduces and the axial buckling wavelength of the cylindrical shell is shorter;relative to thin shell,the thick shell can reduce the degree of influence of the axial pressure on radial buckling pressure.For the study on the dynamic buckling characteristic of the thin-walled stiffened cylindrical shell under the coupling loading of static and dynamic load,the grid stiffened cylindrical shell under the joint action of the axial static pressure and radial uniformly distributed transient external pressure will be taken as the object of study and the numerical method for the dynamic buckling under the coupling loading of static and dynamic load is established and the corresponding experiment is performed to verify the accuracy of the above-mentioned numerical method.The main feature of the experiment is to achieve the joint loading of the axial static pressure and radial transient external pressure of the cylindrical shell through the shock-wave pressure generated by the bolt pre-tightening force and simultaneous blasting of the multi-gasbag powder charge.The coupling loading of the axial static pressure and radial uniformly distributed transient external pressure and dynamic buckling characteristic of the grid stiffened cylindrical shell under the coupling loading of the axial static pressure and radial uniformly distributed transient external pressure are separately studied based on the numerical computation method for the dynamic buckling of cylindrical shell under the coupling loading of the static and dynamic load.For the former,the dynamic buckling characteristic of the cylindrical shell structure under the pulse loading of the radial transient external pressure with different pulse duration and amplitude is studied to determine the Pmax-T critical buckling load line and discuss the influence of the pulse waveform of the axial pressure and radial transient external pressure on the Pmax-T critical buckling load line;the numerical result shows that the structure will have elastic dynamic buckling under the loading with low amplitude and long pulse duration,while the structure mainly has plastic dynamic buckling under the loading with high amplitude and short pulse duration;meanwhile,with the increase of pulse duration,the critical load causing the dynamic buckling of the structure reduces and the number of buckling ripple reduces;when the pulse duration increases to a certain scope,the amplification factor of dynamic buckling approaches to 1 and the corresponding Pmax-T critical buckling load line at this stage approaches to an asymptotic line;the hazardous area of the radial transient external pressure causing the dynamic stability failure of the grid stiffened cylindrical shell structure increases with the increase of the pre-added axis pressure;it is much easier for the pulse wave load of half-sine function to cause the dynamic stability failure of the cylindrical shell structure than the symmetrical triangular pulse wave load.For the latter,the critical radial static pressure value causing the instability of cylindrical shell when there is only impact response or impact damage but no impact buckling under the action of the radial transient external pressure is determined based on the critical excitation.The numerical result shows that when the pulse load of transient external pressure does not cause the dynamic buckling of the grid stiffened cylindrical shell,the larger the impulse or strength of the pulse load is,the smaller the corresponding critical radial static pressure causing the bucking instability of the structure is.