In this paper a robust and effective 4-node shell element for the structural analysis of thin structures is described. A Hu–Washizu functional with independent displacements, stress resultants and shell strains is the variational basis of the theory. Based on a previous paper an additional interpolation part using quadratic shape functions is introduced for the independent shell strains. Especially for unstructured meshes this leads to an improved convergence behavior. The expanded element formulation proves to be insensitive to mesh distortion. Another well-known feature of the mixed hybrid element is the robustness in nonlinear applications with large deformations.

中文翻译：

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基于Hu–Washizu函数的改进的四边形壳单元

在本文中，描述了用于薄结构的结构分析的鲁棒且有效的四节点壳单元。具有独立位移，应力结果和壳体应变的Hu-Washizu泛函是该理论的变分基础。在以前的论文的基础上，介绍了使用二次形状函数的附加插值部分，用于独立的壳应变。特别是对于非结构化网格，这会导致改善的收敛行为。事实证明，扩展元素公式对网格变形不敏感。混合混合元件的另一个众所周知的特征是在具有大变形的非线性应用中的鲁棒性。