Buckling Analysis And Experimental Study Of External Pressure Spherical Shell Head

The spherical head is a widely used pressure resistant structure in the pressure resistant structure of deep-sea pressure submersible,the buckling pressure of spherical head has an important influence on the pressure characteristics of the whole submersible.Therefore,the study on the buckling pressure characteristics of the spherical head has important theoretical significance and practical value to improve the buckling and pressure resistance performance of the deep-sea pressure submersible.Experimental research,theoretical research and numerical analysis are combined to analysis buckling characteristics of spherical shell head,influence of defects on the voltage characteristics,and spherical head buckling characteristics.The main research contents and conclusions are as follows:(1)The comparison between the collapse test and analytical method of the hemispherical head shrinkage model is carried out.The results show that the deviation of the calculated results from the Zoelly formula,the Karman-Tsien Hsueshen formula,the analytical formula of the capacity and the revised formula of the laboratory is the same as that of the experimental value.That is to say,the capability analysis method is better than the large deformation theory for the theoretical buckling analysis of the spherical shell.The calculated results of the laboratory correction formula are close to the experimental values,but the results are still large.So it is necessary to expand the safety factor in design.(2)The perfect geometric linear buckling analysis of the hemispherical head,geometrically nonlinear buckling analysis of the hemispherical head and actual geometric nonlinear buckling analysisof the hemispherical head were carried out by ABAQUS.The results of linear buckling and Zoelly formula are very close to the perfect geometry,but the shape of instability is not consistent with the experimental results.There is a certain gap between the nonlinear buckling and the experimental results under the perfect geometric condition,and the buckling instability is very close.The nonlinear buckling of the material is close to the experimental results,and the buckling instability is the same.(3)The effect of the uniform mode imperfection on the buckling characteristics of hemispherical head is analyzed by ABAQUS.For the perfect geometry,the buckling pressure of the hemispherical head decreases with the increase of the amplitude of the defect,but its sensitivity to the defect decreases with the increase of the amplitude of the defect.For the actual geometry,buckling pressure of hemispherical head decreases with the defect amplitude,but the amplitude effect of defects on buckling capacity of the hemispherical head is either positive or negative,and the initial value is very sensitive to small defects and defects.Therefore,in the process of manufacturing the hemispherical head,in order to ensure that the hemispherical head meets the design of the buckling capacity,it is necessary to strictly control the initial defect.(4)Buckling characteristics of equivalent radius of curvature and equivalent parallel diameter of spherical head were analyzed by ABAQUS.The main characteristics of spherical head buckling have a greater relationship with the curvature radius of spherical curvature radius,the greater the buckling pressure capacity is small.The spherical head for maximum buckling stress and buckling position are located near the bottom of the spherical head region,without big changes in height and curvature radius of spherical cap.Therefore,in thedesigning of spherical head,so that the spherical radius of curvature should be as much as possible,and the area neared the bottom of the spherical head is appropriate to strengthen.