大型薄壁贮箱焊接区等应力优化设计

Stress optimization of the weld zone of large thin-walled tank structures

在内压载荷作用下,大型薄壁贮箱结构圆筒壳与半球壳的变形不协调,导致焊接区有较大弯曲应力,然而采用传统方法难以实现等应力设计。从应力传递的角度来说,消除弯曲应力,就是实现整个截面均匀传力。基于此,本文首先对传统方法设计出的薄壁贮箱焊接区进行有限元分析,获得应力分布规律,发现焊缝附近横向应力的传力路径在焊接区附近完成了从内壁向外壁的改变;然后基于控制传力路径的思想,在焊接区两侧的过渡环和圆筒壳厚区构造削弱槽,以实现焊接区均匀传力;最后采用非支配排序遗传算法进行参数优化,在焊接区获得了较均匀的应力分布。与传统设计方案相比,本文优化设计后的应力梯度降低了80%,应力峰值降低了40%。

While a large thin-walled tank structure is subjected to internal pressure, large local bending moment and stress gradient is formed in the weld zone between the cylinder shell and the semi-spherical shell. It is known that it is difficult to realize the constant strength design through the traditional method. Also, the topological optimization is relatively difficult due to the existence of internal pressure on the design region. In this paper, finite element analysis is conducted to analyze the stress field of the conventional design firstly. It is discovered that there is a change of stress transmission path from the inner wall to the outer wall, which produces a high stress gradient in the weld zone. Secondly, based on the concept of stress transmission path control, two weakened zones are constructed respectively in the transition ring and the thick section of cylinder shell. Then a parameteroptimization model is formed. Finally, Non-dominated Sorting Genetic Algorithm(NSGA) is adopted for the parameter optimization, more uniform stress distribution of the weld zone can be obtained and the stress gradient is reduced by 80% and the maximum stress value is reduced by 40%.