Solid or shell finite elements to model thick cylindrical tubes and shells under global bending
Solid or shell finite elements to model thick cylindrical tubes and shells under global bending
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DOI：
10.1016/j.ijmecsci.2013.05.008
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发表时间：
2013-09
影响因子：
7.3
通讯作者：
A. Sadowski;J. Rotter
中科院分区：
文献类型：
--
作者：
A. Sadowski;J. Rotter
本文探讨了用固体连续有限元和壳有限元模拟圆柱形金属管壳在整体弯曲下的非线性塑性屈曲行为。随着曲率半径与厚度之比的减小，壳体分析的假设变得越来越不确定，但经典文献没有明确界定何时壳体处理是不合适的，何时连续体模型变得必要。这对于管件、管道、烟囱、桩、塔和类似结构的弯曲是一个特别重要的问题。因此，本研究只涉及薄管或厚壳的均匀弯曲，这些薄管或厚壳在应变硬化范围内因塑性屈曲而失效。分析采用有限元公式，可在商业软件ABAQUS，因为这是最广泛使用的工具，在这个领域的参数化研究具有广泛和多样化的元素库。所得结果具有普遍意义，并可用于其它有限元方法。因此，本文旨在确定适当的薄壳或厚壳近似，考虑几何非线性，复杂的平衡路径，极限点和分叉屈曲，广泛的材料延性和线性应变硬化。它的目的是建立时，它是可行的，采用壳单元，当这一决定将导致结果，缺乏足够的精度为工程设计purpose.结果表明，薄和厚（剪切柔性）壳单元可以给出一个合理的准确预测的屈曲力矩下的整体均匀弯曲的圆柱管厚asR/t=10。一个有限的应变和厚壳配方另外示出模型的延展性，这样的厚管，即使当椭圆形的横截面和应变硬化。当R/ratio超过25时，用固体连续体单元模拟管的弯曲，在解的精度和计算时间方面，与壳单元相比，其优点减少了，因而变得越来越不经济。
This paper explores the use of solid continuum finite elements and shell finite elements in the modelling of the nonlinear plastic buckling behaviour of cylindrical metal tubes and shells under global bending. The assumptions of shell analysis become increasingly uncertain as the ratio of the radius of curvature to the thickness becomes smaller, but the classical literature does not draw a clear line to define when a shell treatment is inappropriate and a continuum model becomes essential. This is a particularly important question for the bending of tubular members, pipelines, chimneys, piles, towers and similar structures. This study is therefore concerned solely with the uniform bending of thin tubes or thick shells which fail by plastic buckling well into the strain-hardening range. The analyses employ finite element formulations available in the commercial software ABAQUS because this is the most widely used tool for parametric research studies in this domain with an extensive and diverse element library. The results are of general validity and are applicable to other finite element implementations. This paper thus seeks to determine the adequacy of a thin or thick shell approximation, taking into account geometric nonlinearity, complex equilibrium paths, limit points and bifurcation buckling, extensive material ductility and linear strain hardening. It aims to establish when it is viable to employ shell elements and when this decision will lead to outcomes that lack sufficient precision for engineering design purposes.The results show that both thin and thick (shear-flexible) shell elements may give a reasonably accurate prediction of the buckling moment under global uniform bending for cylindrical tubes as thick asR/t=10. A finite strain and thick shell formulation is additionally shown to model the ductility of such thick tubes well, even when ovalisation of the cross-section and strain hardening are included. The use of solid continuum elements to model tubes in bending is found to become increasingly uneconomical as theR/tratio rises above 25 with reduced advantages over shell elements, both in terms of the accuracy of the solution and the computation time.