关于运动耦合和分布耦合的区别，*KINEMATIC，

ma

*KINEMATIC
Define a kinematic coupling constraint.

还有一个
*KINEMATIC COUPLING
Constrain all or specific degrees of freedom of a set of nodes to the rigid body motion of a reference node
这俩关键字有什么区别
一个运动耦合，一个分布耦合？

dreamlb

我的理解是这样的：
*KINEMATIC COUPLING相当于Nastran中的rbe2，即被约束的节点和主节点自由度是保持一致的，这样会导致局部刚硬。
*DISTRIBUTING COUPLING相当于Nastran中的rbe3，即被约束的节点和主节点分担载荷，具体是怎样分担呢？建立两个平衡方程：力平衡方程和力矩平衡方程。也就是说如果主节点不在从节点的行心位置，可能会产生附加的力矩~
对于需施加位移约束的地方，当然是使用*KINEMATIC COUPLING较好，但是需记住，此处应力不真实，因为局部过硬，好在我们有圣维南原理嘛~如果您对此处应力特别关心，就不能如此简化了。
对于需要施加载荷的地方（如力矩），使用*DISTRIBUTING COUPLING，当然中心点位置尽量在需耦合点的行心。否则会出现虚假的附加力矩。
相对来说，*KINEMATIC COUPLING比DISTRIBUTING COUPLING刚硬，不过两者都是简化，DISTRIBUTING COUPLING用处更广泛，可以用来耦合不同的单元之间的连接。
当然，您也可以再制作更普遍的自由度耦合约束，那就是使用Equation，可以制作更通用的节点之间的自由度约束~
很多时候，这样的自由度耦合是很方便和必要的。比如两个材料相差很大的区域，若直接采用节点重合的方式连接，求解时可能会因为刚度畸变得到很差的结果，这也正是有限元发展mpc的原因之一。

zaw1110

个人感觉，运动耦合和rigid body差不多。表面节点运动与受力相同，且不发生相对位移，运动等等。。
而分布耦合与tie差不多。。受力相同，但是表面节点会发生相对的位移，运动等等。。。

maschinen666

楼主的问题好象有错,运动耦合是*KINEMATIC COUPLING,但是分布耦合是*DISTRIBUTING COUPLING.我也是被这个问题困惑,
因为KINEMATIC 表示的是定义运动耦合约束
*KINEMATIC COUPLING 表示的是：约束所有或指定节点集的自由度来参考一个节点的刚体运动

从字面上我无法理解具体的含义。那位前辈可以举例说明一下,谢谢!

sunset123123

• Kinematic coupling is enforced in a strict master-slave approach. Degrees of freedom (DOFs) at the coupling nodes are eliminated, and the coupling nodes will be constrained to move with the rigid body motion of the reference node.
• Distributing coupling is enforced in an average sense. Degrees of freedom at the coupling nodes are not eliminated. Rather, the constraint is enforced by distributing loads such that: o the resultants of the forces at the coupling nodes are equivalent to the forces and moments at the reference node, and o force and moment equilibrium of the distributed loads about the reference point is maintained.
Usage notes
•
Kinematic coupling is enforced in a strict master-slave approach. Degrees of freedom (DOFs) at the coupling nodes are eliminated, and the coupling nodes will be constrained to move with the rigid body motion of the reference node.
•
Distributing coupling is enforced in an average sense. Degrees of freedom at the coupling nodes are not eliminated. Rather, the constraint is enforced by distributing loads such that:
o
the resultants of the forces at the coupling nodes are equivalent to the forces and moments at the reference node, and
o
force and moment equilibrium of the distributed loads about the reference point is maintained.
Usage notes
•
A kinematic coupling constraint does not allow relative motion among the constrained DOFs. It does allow relative motion among the unconstrained DOFs.
A distributing coupling allows relative motion among the constrained and unconstrained DOFs. The relative motion of the coupling nodes will be such that the equilibrium condition on the distributed loads is maintained.
As an example, consider the cantilever beam shown in Figure 1. It is meshed with second order brick elements and is built-in at the right end. A coupling constraint is defined at the free end. Degrees of freedom 1 through 6 of the end surface nodes are included in the constraint. At the reference node, a displacement is applied in the vertical (2) direction, while all other displacement and rotation components are held to zero.

sunset123123

简单点讲刚性耦合，对于被耦合点之间没有相对的运动，和参考点一起可视为刚性，而运动耦合中的被耦合点之间允许相对变形，是对参考点加载载荷的内部平均话处理。你可以做一个悬臂梁例子来对比一下他们的应力分布。

gizmo

*KINEMATIC 必须与coupling联合使用，不能作为一个独立的关键字。

capicious

好像说得有点问题。看这句话Kinematic coupling is enforced in a strict master-slave approach. Degrees of freedom (DOFs) at the coupling nodes are eliminated....

运动耦合中的被耦合点没有了自由度，怎么允许相对变形呢？

原帖由 sunset123123 于 2008-6-12 09:09 发表
简单点讲刚性耦合，对于被耦合点之间没有相对的运动，和参考点一起可视为刚性，而运动耦合中的被耦合点之间允许相对变形，是对参考点加载载荷的内部平均话处理。你可以做一个悬臂梁例子来对比一下他们的应力分布。

六合音

这位斑竹的回答不太理解，与石亦平老师的《abaqus有限元分析实例详解》这本书上解释的感觉不相符。运动耦合：在此区域的各个节点与参考点之间建立一种运动上的约束关系。
分布耦合：也是在此区域的各个节点与参考点之间建立一种约束关系，但是对此区域上个节点的运动进行了加权平均处理，使此区域上受到的合力和合力矩与施加在参考点上的力和力矩相等效。换言之，分布耦合允许面上的各部分之间发生相对变形，比运动耦合中的面更柔软。
不过对于上面的解释我还是不太理解这两者之间的区别与应用。哪位大侠帮忙详细解释下。。。
5# sunset123123

qishuxue

期待详解！本人亦对运动耦合与分布耦合很困惑！

joybee110

我觉得kinematic　是刚体耦合,意思是耦合区域不能变形
distribute是柔体耦合,可以变形

不知道大家怎么理解的　
还望指教啊

shineee

This is from My Abaqus (www.abaqus.com) pagego and search using "kinematic coupling")
Both types of coupling constraint have the common purpose of coupling the motion of a collection of nodes on a surface (the coupling nodes) to the motion of a reference node. Some differences between the two methods are outlined below.
Nature of the constraint enforcement
Kinematic coupling is enforced in a strict master-slave approach. Degrees of freedom (DOFs) at the coupling nodes are eliminated, and the coupling nodes will be constrained to move with the rigid body motion of the reference node.
Distributing coupling is enforced in an average sense. Degrees of freedom at the coupling nodes are not eliminated. Rather, the constraint is enforced by distributing loads such that:
the resultants of the forces at the coupling nodes are equivalent to the forces and moments at the reference node, and
force and moment equilibrium of the distributed loads about the reference point is maintained.
Usage notes
A kinematic coupling constraint does not allow relative motion among the constrained DOFs. It does allow relative motion among the unconstrained DOFs.
A distributing coupling allows relative motion among the constrained and unconstrained DOFs. The relative motion of the coupling nodes will be such that the equilibrium condition on the distributed loads is maintained.
As an example, consider the cantilever beam shown in Figure 1. It is meshed with second order brick elements and is built-in at the right end. A coupling constraint is defined at the free end. Degrees of freedom 1 through 6 of the end surface nodes are included in the constraint. At the reference node, a displacement is applied in the vertical (2) direction, while all other displacement and rotation components are held to zero.

Figure 1: Cantilever beam, undeformed Figure 2: Cantilever beam, deformed

The model is analyzed using the kinematic and distributing constraint methods. Viewed globally, the deformed shape of the beam for both constraint types is similar, and is shown in Figure 2.

Figure 3: Axial displacement, distributing coupling Figure 4: Axial displacement, kinematic coupling

A closer inspection of the displacements at the coupled end of the beam reveals the difference between the results of the two constraint methods. Figures 3 and 4 show contours of the axial (3-direction) displacement at the free end of the beam for the distributing and kinematic methods, respectively. In both plots, the legend scale has been adjusted to make the displacement gradient more visible. The distributing coupling allows the nodes at the end of the beam to experience relative deformation. The kinematic coupling, because it constrains the motion of the coupling nodes to the rigid body motion of the reference node, does not. The displacement in the axial (as well as lateral) direction is identically zero because of the boundary condition on the reference node.

Continuing with the above example, consider the case when only degrees of freedom 1-3 are coupled; the contours of axial displacement are shown in Figures 5 and 6 for the distributing and kinematic methods, respectively.

Figure 5: Distributing coupling, DOFs 1-3 coupled Figure 6: Kinematic coupling, DOFs 1-3 coupled
Figure 5 shows that with the distributing coupling, the end of the beam is free to rotate. Figure 6 shows that with the kinematic coupling, rotation of the beam end is constrained. The reason is that rotational degrees of freedom at the reference node of a distributing coupling are only active when at least one slave rotational DOF is coupled. In contrast, all degrees of freedom are active at the reference node of a kinematic coupling constraint, independent of the slave DOFs participating in the constraint. Proper constraints must be placed on the unconstrained DOFs of the reference node to avoid numerical singularities.

A kinematic coupling constraint is advantageous when a particular kinematic mode in a structure must be suppressed. An application is the simulation of pure bending in thin-walled pipes, in which the cross section must ovalize but remain plane. The details of this example are outlined in ABAQUS Answer 1139.

A distributing coupling allows more control of the distribution of load from the reference node to the coupling nodes. In addition to a uniform distribution, distributions can be made to decrease linearly, quadratically, or cubically with distance from the reference node. No control is provided with the kinematic method.

The distributing coupling must always constrain all available translational degrees of freedom at the coupling nodes. This is not necessary with the kinematic coupling constraint.

Once any combination of degrees of freedom at the coupling nodes is specified in a kinematic coupling constraint, none of the remaining degrees of freedom are available for further constraint. This is not the case for the distributing coupling. Additional details are provided in ABAQUS Answer 1125.

For either type of constraint, concentrated loads or displacements can be applied at the reference node.
A large number of coupling nodes in a distributing coupling definition can cause excessive memory usage and long run times; this is a result of the large wavefront that is produced when forming the constraint.
Defining constraints in ABAQUS/CAE
Coupling constraints are defined in the Interaction module of ABAQUS/CAE. First define the surface to be coupled. Then, if the reference node is not part of the existing geometry, a separate reference node must be created (Tools ® Reference Point). Then select:
Constraint ® Create... ® Coupling ® select the reference node ® select the coupling surface
The Edit Constraint dialog box will appear, from which the constraint type and coupled degrees of freedom can be selected.
这是网上搜到的，但是我在ABAQUS网站没搜到该贴原版。
再发一个Su斑竹旧帖，可能更有利于理解：
Kinematic coupling constraints被coupling的node的自由度,會被reference node所控制, coupling node之間不會有相對移動或轉動(在standard code的情況下絕對成立,在explicit code下kinematic coupling constrains則是使用penalty method,施力過大或過於激烈仍會有相對運動).; k# w1 D" y6 f; G# w6 a
Distributing coupling constrains則是使施加在reference point上的force或monent平均分配到coupling node上,所以cpupling node之間允許相對運動,而這種拘束方式由於需要計算coupling node的force 與monent,因此計算量大增.
由於coupling constraints是簡化model的方式,用在需要傳力但不關心應力之處,因此一般建議不需使用Distributing coupling constrains.