常用结构单元有哪些？你需要这篇文章！

    翻开ANSYS官方帮助文档，会看到很多单元类型。即使只关注结构分析领域，结构单元的类型也很多。

    这个世界上，很多事物符合二八定律。单元的应用范围也不例外，可以说结构单元的类型虽然多，但常用的不多，本文介绍如下单元。

01 常用结构单元

    杆单元-LINK180

    索单元-CABLE280

    管单元-PIPE288

    梁单元-BEAM188

    平面单元-PLANE183

    壳单元-SHELL181

    体单元-SOLID186

    体单元-SOLID187

02 线单元

   杆单元：LINK180单元，有2个节点，每个节点有3个平移自由度。

    The element is a uniaxial tension-compression element with three degrees of freedom at each node: translations in the nodal x, y, and z directions.

   索单元：CABLE280单元，有3个节点，每个节点有3个平移自由度。

    CABLE280 is suitable for analyzing moderate to extremely slender cable structures (such as undersea cables). The element is a quadratic three-node line element in 3D space. Each node has three degrees of freedom: translations in the nodal x, y, and z directions.

   管单元：PIPE288单元，有2个节点，每个节点有3个平移自由度和3个转动自由度。

    The element has six degrees of freedom at each node (the translations in the x, y, and z directions and rotations about the x, y, and z directions). 

   梁单元：BEAM188单元，有2个节点，每个节点有3个平移自由度和3个转动自由度。另外，还有1个翘曲自由度可选。

    BEAM188 has six or seven degrees of freedom at each node; these include translations in the x, y, and z directions and rotations about the x, y, and z directions. A seventh degree of freedom (warping magnitude) is optional.

03 平面单元

   平面单元：PLANE183单元，有8个节点(可以退化为6个)，每个节点有2个平移自由度。当作为考虑扭矩的轴对称单元时，每个节点有2个平移自由度和1个转动自由度。

    This element is defined by eight nodes or six nodes. It can be used as a plane element (plane stress, plane strain and generalized plane strain) or as an axisymmetric element (with or without torsion). In most cases, the element has two degrees of freedom at each node: translations in the nodal x and y directions. For the axisymmetric with torsion option, however, the element has three degrees of freedom at each node: translations in the nodal x and y directions and rotation in the nodal y direction.

04 壳单元

   壳单元：SHELL181单元，有4个节点(可以退化为3个)，每个节点有3个平移自由度和3个转动自由度。当作为薄膜单元时，每个节点只有3个平移自由度。

    It is a four-node element with six degrees of freedom at each node: translations in the x, y, and z directions, and rotations about the x, y, and z-axes. (If the membrane option is used, the element has translational degrees of freedom only).

05 体单元

   体单元：SOLID186单元，有20个节点(可以退化为10个、13个、15个)，每个节点有3个平移自由度。

    The element is defined by 20 nodes having three degrees of freedom per node: translations in the nodal x, y, and z directions. 

   体单元：SOLID187单元，有10个节点，每个节点有3个平移自由度。

    The element is defined by 10 nodes having three degrees of freedom at each node: translations in the nodal x, y, and z directions. 

06 附录

   管单元：PIPE289单元，有3个节点，每个节点有3个平移自由度和3个转动自由度。PIPE288的高阶单元。

    The element has six degrees of freedom at each node (the translations in the x, y, and z directions and rotations about the x, y, and z directions)

   梁单元：BEAM189单元，有3个节点，每个节点有3个平移自由度和3个转动自由度。另外，还有1个翘曲自由度可选。BEAM188的高阶单元。 

    With default settings, six degrees of freedom occur at each node; these include translations in the x, y, and z directions and rotations about the x, y, and z directions. An optional seventh degree of freedom (warping magnitude) is available. 

   壳单元：SHELL281单元，有8个节点(可以退化为6个)，每个节点有3个平移自由度和3个转动自由度。当作为薄膜单元时，每个节点只有3个平移自由度。SHELL181的高阶单元。 

    The element has eight nodes with six degrees of freedom at each node: translations in the x, y, and z axes, and rotations about the x, y, and z-axes. (When using the membrane option, the element has translational degrees of freedom only.)

   体单元：SOLID185单元，有8个节点(可以退化为6个、4个、5个)，每个节点有3个平移自由度。 SOLID186的低阶单元。

    It is defined by eight nodes having three degrees of freedom at each node: translations in the nodal x, y, and z directions.

    另外，结构仿真分析中，还有一些单元也很常用，但它们并不属于结构本身，只是为了实现某些特殊的功能。比如：

    1）弹簧单元用于模拟弹簧连接；

    2）质量单元用于考虑质量效应；

    3）接触单元用于定义结构之间的连接关系；

    4）MPC184单元用于定义结构之间的运动关系；

    5）表面效应单元主要用于定义载荷;