周边夹持大应变金属薄膜变形特性有限元分析

FINITE ELEMENT ANALYSIS FOR THE BULGING BEHAVIORS OF CLAMPED METALLIC DIAPHRAGMS WITH FINITE STRAINS

受侧向载荷作用的金属薄膜可作为一种功能元件用于防止装置超压或实现某些特定的工艺操作 ,在许多行业被大量使用。几何和材料非线性的特点使得解析计算非常困难 ,目前其设计和制造主要依赖于实验。文中采用MITC4(mixedinterpolationoftensorialcomponents)壳元基于T L (TotoalLagrange)列式 ,对普通和开有透缝的二种结构形式的金属薄膜进行有限应变弹塑性有限元分析。通过与实验结果的比较 ,得出如下的结论 ,①普通膜的高应力应变区位于极顶附近约 1 3口径的区域 ,应力梯度自周边向内不断减弱。②极顶挠曲高度随加载呈弱“S”形的规律变化。③随加载 ,横向塑性应变的变化过程可以划分为缓慢增加段、过渡段和快速增加段 3个阶段 ,阶段的 2个分界点为pa s0 ≈ 5 3 0MPa和 880MPa。④透缝膜高应力应变区位于内圈终止小孔孔桥间的边缘局部区域。⑤存在一个重要的数群pa (s0 b) ,不同d时最大等效应力相对于该数群具有十分相近的变化规律。

Metallic diaphragms under lateral pressure are widely used to protect equipments from overpressure or to meet some particular needs of technical processes. Due to the nonlinear behaviors in both geometry and material, it is very difficult to get analytic resolution. The design and fabrication are now intensively depending upon experiments. Based on MITC4(mixed interpolation of tensorial components) shell element and T.L.(Totoal Lagrange) formulations, finite element analysis was made for ordinary membranes and radial slot diaphragms. The obtained results showed good agreements with the measured results. The conclusions are as follows: ① For ordinary diaphragms, the area of highest stresses and biggest strains is located in the central region of about 1/3 diameter of the hatch, and stress gradient is gradually decreased in radial inward direction. ② The deflection at the crown is increased in a trend of weak sigmoid shape. ③ The increasing of transverse plastic strain at the crown can be divided into three stages of slow stage, transitional stage and fast stage. Two division points are at about 530*!MPa and 880*!MPa of the pa/s 0. ④ For slot diaphragms, the highest stress and strain focus on the small areas located on the margin of pinholes in the direction of bridge. ⑤ The pa/(s 0b) has significant meaning. For the different inner diameter, it's found that the maximum equivalent stresses show nearly coincident variety rule relative to pa/(s 0b).