罕见议题！Mechanical的五种接触模型

    本文讨论的不是接触类型！大多数用户对接触类型比较熟悉。接触类型可以分为线性接触和非线性接触。线性接触可以分为绑定(Bonded)和不分离(No Separation)；非线性接触可以分为无摩擦(Frictionless)，粗糙(Rough)，摩擦(Frictional)。(强制摩擦滑动，Forced Frictional Sliding，只支持刚体动力学)。

    本文讨论的是接触模型！一字之差。接触模型是指接触对象的类型。

    面元素-Face：3D实体的面，壳面。线元素-Edge：3D实体的线，壳面的线，2D实体的线，线体的线。点元素-Vertex：3D实体的点，壳面的点，2D实体的点，线体的点。

    这些几何元素之间的接触关系应该选择什么样的接触模型来模拟。比如，壳面和实体面的接触，壳线和实体面的接触，壳线和壳线的接触等等。这个问题似乎并不简单。

    Five contact models are available: node-to-node, node-to-surface, surface-to-surface, line-to-line, and line-to-surface.

    Mechanical有五种接触模型可用：节点到节点、节点到面、面到面、线到线、线到面。

    Node-to-node contact elements, CONTA178, are typically used to model point-to-point contact applications. To use node-to-node contact elements, you need to know the location of contact beforehand. 

节点到节点接触单元 CONTA178， 通常用于模拟点到点接触。使用节点到节点的接触单元，需要事先知道接触的位置。

    Node-to-node contact elements can also be used to solve a surface-to-surface problem if the nodes of the two surfaces line up, the relative sliding deformation is negligible, and deflections (rotations) of the two surfaces remain small.

    如果两个面的节点对齐、相对滑动变形可忽略且两个面的偏转（旋转）保持很小，则节点到节点接触单元也可用于解决面到面问题。

    Another use of node-to-node contact elements is in extremely precise analysis of surface stresses, such as in turbine blade analysis.

    节点到节点接触单元的另一个用途是极其精确的表面应力分析，例如涡轮叶片分析。

    In addition to unidirectional contact behavior, CONTA178 offers a cylindrical gap option to model contact between two parallel pipes with small relative sliding. The two pipes can be adjacent to one another, or one pipe can be inside of another hollow pipe. Also, CONTA178 can model contact between two rigid spheres; this can be either two adjacent spheres or one sphere inside of a hollow sphere.(For large sliding applications, see 3-D Line-to-Line Contact.) 

    除了单向接触行为外，CONTA178 还提供圆柱形间隙选项来模拟两个平行管道之间的接触，且相对滑动较小。两个管子可以彼此相邻，或者一个管子可以在另一个中空管子的内部。此外，CONTA178 可以模拟两个刚性球体之间的接触；可以是两个相邻的球体或空心球体内部的一个球体。（对于大型滑动应用，请参见 3-D 线对线接触。）

    CONTA175 is a node-to-surface contact element.  CONTA175 is typically used to model point-to-surface contact applications, such as the corners of snap-fit parts sliding along the mating surface.

    节点到面的接触单元CONTA175。CONTA175 通常用于模拟点对面接触应用，例如沿配合面滑动的卡扣零件的角。

    You can also use CONTA175 to model surface-to-surface contact, if the contacting surface is defined by a group of nodes and multiple elements are generated. The surfaces can be either rigid or deformable. 

    如果接触面由一组节点定义并且生成了多个单元，还可以使用 CONTA175 来模拟面到面接触。面可以是刚性的或可变形的。

    Unlike the node-to-node contact elements, you do not need to know the exact location of the contacting area beforehand.

    与节点到节点接触单元不同，不需要事先知道接触区域的确切位置。

    CONTA175 does not support 3-D higher-order elements on the contact surface side. The element can fail if the target surface is severely discontinuous. No contour plots are available for contact results.

    CONTA175 不支持接触面侧的 3-D 高阶元素。如果目标面严重不连续，则该单元可能会失效。没有可用于接触结果的等高线图。

    The target surface is modeled with either TARGE169 or TARGE170 (for 2-D and 3-D, respectively).The contact surface is modeled with elements CONTA172 or CONTA174.

    目标面使用 TARGE169 或 TARGE170（分别用于 2-D 和 3-D）建模。接触面使用单元 CONTA172 或 CONTA174 建模 .

    The surface-to-surface contact elements have several advantages 

    面到面接触单元有几个优点。

    Support lower and higher order elements on the contact and target surfaces (in other words, corner-noded or midside-noded elements).Provide better contact results needed for typical engineering purposes, such as normal pressure and friction stress contour plots.Have no restrictions on the shape of the target surface. Surface discontinuities can be physical or due to mesh discretization.Allow modeling of fluid pressure penetration loads.

    支持接触面和目标面上的低阶和高阶单元（换句话说，角节点或中节点元素）。提供典型工程目的所需的更好的接触结果，例如法向压力和摩擦应力等值线图。对目标面的形状没有限制。表面不连续性可以是物理的或由于网格离散化。允许对流体压力穿透载荷进行建模。

    The contact line element, CONTA177, is typically used to model 3-D beam-to-beam contact (crossing beams or beams that are parallel to each other) or a pipe sliding inside another pipe. Some practical applications are woven fabric and tennis racquet strings.

    接触线单元 CONTA177 通常用于模拟 3-D 梁与梁接触（交叉梁或彼此平行的梁）或在另一个管道内滑动的管道。一些实际应用是机织织物和网球拍线。

    CONTA177 can be attached to 3-D beam or pipe elements and supports both low-order and higher-order elements on the contact surface. The target surface is modeled with 3-D line segments (TARGE170 straight line or parabolic line elements). 

    CONTA177 可以附加到 3-D 梁或管道单元，并支持接触面上的低阶和高阶单元。目标面使用 3-D 线段（TARGE170 直线或抛物线元素）建模。

    You can use the 3-D line-to-surface contact element, CONTA177, to model flexible-flexible or rigid-flexible contact between a 3-D beam and a surface or between a shell edge (or feature edge of a solid body) and a surface. CONTA177 can also model a combination of 3-D beam-to-surface contact and 3-D beam-to-beam contact when the target surface consists of both surface and line segments.

    可以使用 3-D 线到面接触单元 CONTA177 来模拟 3-D 梁与面之间或壳边（或实体边）与面之间的柔性-柔性或刚性-柔性接触。当目标面由面和线段组成时，CONTA177 还可以模拟 3-D 梁与面接触和 3-D 梁与梁接触的组合。