拟协调轴对称三结点退化壳单元

结合拟协调有限元方法和退化壳有限元概念，构造了一个轴对称三结点退化壳单元，采用了整体，局部和等参三个坐标系，使用与拟协调单元列式方法等效的基于胡－鹫津广义为分原理的杂交／混合单元列式方法构造轴对称三结点退化壳单元；使用相同的等参坐标插值来假设应力和应变，插值既考虑到低阶项的完备，又借鉴了拟协调九结点四边形爱化壳单元的结构经验。为了确定应力应变的插值形式，进行了多次数值试验和单元刚度矩阵的特征值分析

Quasi Conforming Axisymmetric Three Node Degenerated Shell Element

Combined the quasi conforming FEM with the concept of degenerated shell element, an axisymmetric three node degenerated shell element is constructed. The global, the local and the isoparametric coordinate systems are used. The axisymmetric three node degenerated shell element is constructed by using the hybrid/mixed element formulation based the Hu Washizu generalized variational principle which is equivalent to the quasi conforming element formulation. The stress and the strain are assumed by using the same isoparametric coordinate interpolation. In the interpolation, the completeness of low order terms is considered and the experience of constructing the quasi conforming nine node quadrilateral shell element is used for reference. To define the interpolation forms of the stress and the strain, a lot of numerical trials and analysis for eigenvalues of the element stiffness matrix are carried out. The constructed element has no extra zero modes and is free from locking phenomena. The numerical example indicates that the element is accurate and effective. It can be used for the structural analysis of axisymmetric shells in engineering.