基于弧长法的受压球壳稳定性分析

对受压球壳进行特征值屈曲分析,得到了前6阶屈曲模态及线性屈曲临界载荷;采用弧长法进行非线性有限元分析,对理想球壳施加初始扰动,通过2次扰动值折半的方法求得引起结构屈曲的最小扰动值,追踪到了屈曲分支点和全过程载荷-位移路线。基于前6阶屈曲模态位移,在受压球壳中分别引入2.5mm和1mm两种缺陷值,分析缺陷对球壳屈曲特性的影响。结果表明:取壳厚的0.5%即0.05mm时,得最小扰动值,近似模型与完善结构极值载荷的差值为0.93%;球壳是缺陷敏感性结构,缺陷的幅值和分布都对其极限载荷有影响,缺陷幅值与厚度比为0.1时,缺陷球壳承载力相对理想结构下降了约11%,缺陷幅值与厚度比为0.25时,承载力相对下降了约30%,说明提高球壳稳定性需要提高球壳加工精度。

Stability analysis of spherical pressure hull based on arc length method

The buckling of spherical pressure hull is analyzed and the first 6 buckling modes and the liner critical buckling loads are obtained.Nonlinear finite element analysis is performed on the structure using arc length method combined with an initial disturbance.Minimum disturbance which can exactly bring out buckling is obtained by a disturbance binary search method.Bifurcation point and load-displacement path of the whole buckling process is tracked.Considering configurations of the first 6 buckling modes,two values of imperfection which is 2.5mm and 1mm are imported in pressure spherical shell for investigating the influence of imperfection on buckling behavior.The results show that:the minimum disturbance value is 0.05mm which is 0.5% of shell thickness.The difference of the critical buckling loads via approximate model and the perfect structure,respectively,is 0.93%.As an imperfection sensitive structure,the critical buckling load of spherical hull is influenced by amplitude and distribution of imperfection.When the ratio of imperfection value to radius is 0.1,the ultimate bearing capacity of defect spherical hull diseases about 11% compared to ideal structure,and ultimate bearing capacity diseases about 30% when the ratio of imperfection value to radius is 0.25.The manufacturing accuracy of spherical shell should be improved for the purpose of increasing stability.