Abstract: Eccentricity problem occurred during metallic diaphragms for tanks expulsion test is likely to cause gas mixed with liquid and leakage of propellant. In order to solve the eccentricity problem of diaphragms, diaphragms expulsion process was numerically analyzed by Finite Element Method (FEM).Marked numerical eccentricity phenomena was obtained by means of elasto-plasticity constitution model, and the maximum numerical eccentricity value was about 60mm. Numerical eccentricity phenomena caused by using elasto-plasticity constitution model was consistent with that happened during diaphragms expulsion test. Methods of modifying height of cone section and diaphragm thickness, ring-stiffened on diaphragms were raised to improve eccentricity problem and the results of different methods to improve numerical eccentricity phenomena were obtained. Research conclusions indicate that modifying diaphragm thickness is the best method among the three, but the method will significantly increase buckling load and structural mass,while modifying height of cone section follows the first method, but optimal height of cone section should regulate according to radius of arc section.Ring-stiffened on diaphragm ranks the end, but the method can be universally used to improve eccentricity problem of diaphragms, and it can not increase structural mass much. 

Key words: Metallic diaphragms for tanks; Eccentricity problem; Ring-stiffened; Arc length method; Finite element method

摘要： 金属贮箱膜片翻转试验中出现的偏心问题,易造成气液掺混、推进剂泄露等严重后果。为解决膜片的偏心问题,数值计算膜片翻转过程,通过加入弹塑性本构模型引入了显著的数值偏心现象,膜片的最大偏心量约为60mm,且其偏心表现形式与试验中的偏心形式一致性好。提出了改变锥段高度与膜片厚度、环向加筋等方法解决偏心问题,得出了不同方法对数值偏心现象的改善结果。研究表明:增加膜片厚度改善偏心问题效果最好,但同时会显著提高膜片的屈曲载荷与结构质量；改变锥段高度方法次之,但最优锥段高度需根据膜片圆弧旋转段半径进行相应调整；环向加筋方法稍差,但通用性好,且不会显著提高结构质量。 

关键词: 金属贮箱膜片;偏心问题;加筋;弧长法;有限元法 