筒段边界对大直径贮箱椭球箱底的内压稳定性影响研究

Impact study of shell segment boundary on internal pressure stability of the large diameter tank ellipsoid bottom

基于薄膜理论得到的椭球箱底应力分布没有考虑筒段边界的影响,不能真实反映椭球箱底/筒段结构的应力状态。利用有限元方法得到大直径贮箱椭球底/筒段结构的临界失稳载荷及负应力分布,同时进行材料的线性和非线性稳定性计算,得到椭球底/筒段结构的弹性和塑性临界屈曲模数。研究结果表明:筒段边界对椭球箱底环向屈曲存在抑制作用,筒段边界的存在导致箱底弹性临界失稳载荷较理论值偏大22.5%,环向负应力区域会向箱底顶端方向偏移,最大值出现在箱底赤道线偏上;椭球底/筒段结构的弹性临界屈曲模数为1.52,较理论值1.414大7.5%;材料进入塑性后,塑性变形将有助于缓解椭球箱底/筒段结构的塑性屈曲,塑性临界屈曲模数将高于弹性临界屈曲模数。

Based on the membrane theory, the obtained ellipsoid bottom stress distribution does not consider the effect of shell segment boundary, and it can＇t reflect the stress state of ellipsoid bottom/shell segment structure. By using the finite element method, the buckling critical load and negative stress distribution of large diameter tank ellipsoid bottom/shell segment structure were analyzed in this paper. Through the linear and nonlinear material buckling analyses, the elastic and plastic critical buckling moduluses of the ellipsoid bottom/shell segment structure were got. The following conclusions can be drawn from the analysis results. The shell boundary can cause the inhibition of circular buckling on the ellipsoid bottom, and the elastic critical buckling load of the ellipsoid bottom is 22.5% larger than the theoretical value, the circular negative stress zone shifts toward the bottom top, the maximum value appears above the equator line of tank bottom. The elastic critical buckling modulus of ellipsoid bottom/ shell segment structure is 1.52, which is 7.5% larger than the theoretical value 1.414. After material enters into plastic , the plastic buckling of ellipsoid bottom/ shell segment structure is alleviated for plastic deformation, and the plastic critical buckling modulus is bigger than the elastic critical buckling modulus.