自适应有限元分析的降阶单元:研究现状与进展

THE STATE-OF-ART AND RECENT PROGRESSES OF THE REDUCED ELEMENT METHOD

  • 摘要: 新近提出的降阶单元,将有限元常规多项式单元解答的最高次项视为误差项,当作内置的最大模误差估计器;将降低一次的降阶解作为最终解,无需额外计算便可同时完成问题求解和误差计算,一举实现了按最大模控制误差的自适应有限元算法。降阶单元最初针对结构时程分析的自适应步长算法提出,相继将其推广到一般的一维初值、边值问题和二维边值问题,构造了任意四边形降阶单元、三角形降阶单元和时空降阶单元,已成功求解了一大批线性和非线性二维边值问题以及时间空间耦合问题。近期,又在双验法(先验加后验)自适应分析、时空问题合并单元技术和C1薄板弯曲降阶单元三个方面取得了初步的最新进展。该文对这一系列研究进展做一综述性评述,对三方面的最新进展做一简要报道,并给出典型数值算例进一步展现该法的简易性、有效性、通用性和可靠性。

     

    Abstract: The recently proposed reduced element method treats the highest-degree term in the conventional polynomial finite element (FE) solution as an error term, serving as a built-in maximum-norm error estimator. By taking the reduced solution (one degree lower) as the final solution, it simultaneously accomplishes problem solving and error evaluation without additional computations, thus achieving an adaptive FE algorithm that controls errors in the maximum norm. Initially developed for adaptive time-stepping algorithms in structural dynamic analysis, the reduced element was soon extended to two-dimensional boundary value problems (BVPs), where quadrilateral and triangular reduced elements, as well as space-time reduced elements, were constructed. Recently, preliminary progress has been made in three key areas: adaptive analysis using the dual error estimates (a priori plus a posteriori), the element-merging technique for space-time problems, and C1 reduced elements for thin plate bending. This paper provides a comprehensive review of these research developments, briefly reports on the latest advancements in the three aspects and presents representative numerical examples to demonstrate the method's simplicity, effectiveness, generality, and reliability.

     

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