内压作用下压力容器封头局部屈曲分析

LOCALIZED BUCKLING OF TO-RISPHERICAL END CLOSURES UNDERINTERNAL PRESSURE

采用有限元法分析了蝶形封头压力容器在内压作用下封头过渡区局部塑性屈曲问题。通过在内压作用下周向呈受压状态的局部区域引入以静力位移为基础的初始几何缺陷,采用由位移控制的RIKS算法计算跟踪载荷—变形情况,从而分析屈曲载荷和屈曲形态。计算分析了初始缺陷的幅值对所求得的屈曲载荷的影响,结果表明对于所提出的问题,屈曲载荷对初始几何缺陷比较敏感。在屈曲发生后随着加载过程的继续,在过渡区内屈曲区将逐渐增加,即逐渐出现多处皱褶。同时分析了设置多个分布缺陷的情况,与仅有一个缺陷的情况相比,结果显示当缺陷密度不是很密时,从加载初期到初始屈曲发生后的一定范围内,屈曲发生处的变形状态在两种情况下几乎一致,表明初始屈曲非常局部化。

The localized plastic buckling occurred in the transi-tion region in the torispherical end closure of a pressure vessel is analyzed by FEM. By introducing the initial geometrical imperfection, which is determined from the elasto-static dis-placements, into the zone where it is circumferentially com-pressed, the arc-length method RIKS procedure is employed to simulate the deformation process during loading. The buckling point is captured from the load-deflection curve of a typical point within the buckled zone, and the corresponding buckling load is calculated. The results show that the buckling load is quite sensitive to the artificial geometrical imperfections. Fur-thermore, after the first buckling initiated, the succeeding load-ing will lead to more wrinkles within the compressive transition region. Additionally, the case that with four distributed imper-fections is also analyzed. It can be seen that the interaction be-tween the imperfections is very weak before or even after the first buckling occurred, which means the buckling is fairly lo-calized.