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1、ABAQUS/Standard 基础教程,Element Selection Criteria,Appendix 1,ABAQUS/Standard 基础教程,内容提要,Elements in ABAQUS Structural Elements (Shells and Beams) vs. Continuum Elements Modeling Bending Using Continuum Elements 用实体单元模拟弯曲 Stress Concentrations 应力集中 Contact 接触 Incompressible Materials 不可压缩材料 Mesh Generat
2、ion 网格生成 Solid Element Selection Summary,ABAQUS/Standard 基础教程,Elements in ABAQUS,ABAQUS/Standard 基础教程,Elements in ABAQUS,ABAQUS单元库中提供广泛的单元类型，适应不同的结构和几何特征The wide range of elements in the ABAQUS element library provides flexibility in modeling different geometries and structures. Each element can be
3、characterized by considering the following:单元特性： Family 单元类型 Number of nodes 节点数 Degrees of freedom 自由度数 Formulation 公式 Integration 积分,ABAQUS/Standard 基础教程,单元类型（Family） A family of finite elements is the broadest category used to classify elements. 同类型单元有很多相同的基本特。Elements in the same family share ma
4、ny basic features. 同种类单元又有很多变化：There are many variations within a family.,Elements in ABAQUS,special-purpose elements like springs, dashpots, and masses,continuum (solid elements),shell elements,beam elements,rigid elements,membrane elements,truss elements,infinite elements,ABAQUS/Standard 基础教程,Elem
5、ents in ABAQUS,Number of nodes节点数(interpolation) An elements number of nodes determines how the nodal degrees of freedom will be interpolated over the domain of the element. ABAQUS includes elements with both first- and second-order interpolation. 插值函数阶数可以为一次或者两次,ABAQUS/Standard 基础教程,Elements in ABA
6、QUS,自由度数目Degrees of freedom The primary variables that exist at the nodes of an element are the degrees of freedom in the finite element analysis. Examples of degrees of freedom are: Displacements 位移 Rotations 转角 Temperature 温度 Electrical potential 电势,ABAQUS/Standard 基础教程,公式Formulation The mathemati
7、cal formulation used to describe the behavior of an element is another broad category that is used to classify elements. Examples of different element formulations: Plane strain 平面应变 Plane stress 平面应力 Hybrid elements 杂交单元 Incompatible-mode elements 非协调元 Small-strain shells 小应变壳元 Finite-strain shells
8、 有限应变壳元 Thick shells 后壳 Thin shells 薄壳,Elements in ABAQUS,ABAQUS/Standard 基础教程,积分Integration 单元的刚度和质量在单元内的采样点进行数值计算，这些采样点叫做“积分点” The stiffness and mass of an element are calculated numerically at sampling points called “integration points” within the element. 数值积分的算法影响单元的行为The numerical algorithm us
9、ed to integrate these variables influences how an element behaves. ABAQUS包括完全积分和减缩积分。ABAQUS includes elements with both “full” and “reduced” integration.,Elements in ABAQUS,ABAQUS/Standard 基础教程,Full integration:完全积分 The minimum integration order required for exact integration of the strain energy fo
10、r an undistorted element with linear material properties. Reduced integration:简缩积分 The integration rule that is one order less than the full integration rule.,Elements in ABAQUS,ABAQUS/Standard 基础教程,Elements in ABAQUS,Element naming conventions: examples 单元命名约定,B21: Beam, 2-D, 1st-order interpolatio
11、n,CAX8R: Continuum, AXisymmetric, 8-node, Reduced integration,DC3D4: Diffusion (heat transfer), Continuum, 3-D, 4-node,S8RT: Shell, 8-node, Reduced integration, Temperature,CPE8PH: Continuum, Plane strain, 8-node, Pore pressure, Hybrid,DC1D2E: Diffusion (heat transfer), Continuum, 1-D, 2-node, Elect
12、rical,ABAQUS/Standard 基础教程,Elements in ABAQUS,ABAQUS/Standard 和 ABAQUS/Explicit单元库的对比 Both programs have essentially the same element families: continuum, shell, beam, etc. ABAQUS/Standard includes elements for many analysis types in addition to stress analysis: 热传导, 固化soils consolidation, 声场acousti
13、cs, etc. Acoustic elements are also available in ABAQUS/Explicit. ABAQUS/Standard includes many more variations within each element family. ABAQUS/Explicit 包括的单元绝大多数都为一次单元。 例外: 二次单元和四面体单元 and 二次 beam elements Many of the same general element selection guidelines apply to both programs.,ABAQUS/Standa
14、rd 基础教程,Structural Elements (Shells and Beams) vs. Continuum Elements,ABAQUS/Standard 基础教程,Structural Elements (Shells and Beams) vs. Continuum Elements,实体单元建立有限元模型通常规模较大，尤其对于三维实体单元 如果选用适当的结构单元 (shells and beams) 会得到一个更经济的解决方案 模拟相同的问题，用结构体单元通常需要的单元数量比实体单元少很多 要由结构体单元得到合理的结果需要满足一定要求： the shell thickne
15、ss or the beam cross-section dimensions should be less than 1/10 of a typical global structural dimension, such as: The distance between supports or point loads The distance between gross changes in cross section The wavelength of the highest vibration mode,ABAQUS/Standard 基础教程,Shell elements Shell
16、elements approximate a three-dimensional continuum with a surface model. 高效率的模拟面内弯曲Model bending and in-plane deformations efficiently. If a detailed analysis of a region is needed, a local three-dimensional continuum model can be included using multi-point constraints or submodeling. 如果需要三维实体单元模拟细节可以使用子模型,Shell model of a hemispherical dome subjected to a projectile impact,Structural Elements (Shells and Beams) vs. Continuum Elements,ABAQUS/Standard 基础教程,Structural Elements (Shells and Beams) v
