An isogeometric finite element formulation for geometrically and materially nonlinear Timoshenko beams is presented, which incorporates in-plane deformation of the cross-section described by two extensible director vectors. Since those directors belong to the space ${\Bbb R}^3$, a configuration can be additively updated. The developed formulation allows direct application of nonlinear three-dimensional constitutive equations without zero stress conditions. Especially, the significance of considering correct surface loads rather than applying an equivalent load directly on the central axis is investigated. In various numerical examples exhibiting large deformations, the accuracy and efficiency of the presented beam formulation is assessed in comparison to brick elements. We particularly use hyperelastic materials of the St.$\,$Venant-Kirchhoff and compressible Neo-Hookean types.
翻译:提出了几何和物质上非线性Timoshenko波束的等离子计量有限要素配方,其中包括两个可扩展的导体矢量描述的横截面在平面上的变形。由于这些导体属于面积$_Bbb R ⁇ 3美元,因此可以对配置进行添加更新。开发的配方允许直接应用非线性三维构成方程式,而没有零压力条件。特别是,对考虑正确表面负荷而不是直接在中央轴上应用同等负荷的重要性进行了调查。在显示大变形的各种数字实例中,与砖块元素相比,对显示的波束配方的准确性和效率进行了评估。我们特别使用了St.$\\,$Venant-Kirchoff和可压缩的Ne-Hookean型超弹性材料。