求助请高手帮忙看看这个模型如何施加约束和定义接触对（问题不太好描述）
一铜块圆筒，被等份的分为4个铜块，围起来就是一圆筒。圆筒的外面裹着一层很薄的橡胶套。铜块和橡胶套以相同的转速旋转，在离心力的作用下，四个铜块同时向外推动橡胶变形，每个铜块始终接触橡胶套。整个模型的对称轴是z轴橡胶非常薄，因此我选用了壳单元shell181，铜块用solid45，分别建立四个接触对，但是用接触向导也就是GUI的方式定义接触对时，提示： *** WARNING *** CP = 38.406 TIME= 11:30:51
All selected contact pairs are initially open.Rigid body motion can
occur.You may use auto CNOF/ICONT by setting KEYOPT(5) to close
small gaps.
*** WARNING *** CP = 38.594 TIME= 11:30:51
The only selected contact pair is initially open.Rigid body motion
may occur in any portion of the model held in place solely by contact
elements.
为了让四个铜块能够同步向外推动橡胶，切换坐标系为柱坐标系，并把所有节点旋转到当前的柱坐标系下，将四个铜块的内表面的节点耦合了x方向的自由度（命令preprocessor>coupling>ceqn>coupleDOFs）。然后切换到直角坐标系，并把所有节点旋转到直角坐标系，在z轴方向施加整体角速度100（命令OMEGA,0,0,100,0） 其他没有施加任何约束。
设置求解后出现
*** WARNING *** CP = 68.391 TIME= 11:36:23
No constraints have been defined using the D command.
*** WARNING *** CP = 141.156 TIME= 11:40:39
There are 10 small equation solver pivot terms.
*** WARNING *** CP = 229.469 TIME= 11:49:57
There are 1 small equation solver pivot terms.
*** WARNING *** CP = 313.344 TIME= 11:58:13
There are 6 small equation solver pivot terms.
*** WARNING *** CP = 388.703 TIME= 12:07:38
There are 257 small equation solver pivot terms.
*** ERROR *** CP = 389.141 TIME= 12:07:48
The value of UY at node 21249 is 4.512153122E+09.It is greater than
the current limit of 1000000.This generally indicates rigid body
motion as a result of an unconstrained model.Verify that your model
is properly constrained.
*** ERROR *** CP = 389.641 TIME= 14:26:50
*** MESSAGE CONTINUATION ---- DIAGNOSTIC INFORMATION ***
If one or more parts of the model are held together only by contact
verify that the contact surfaces are closed.You can check contact
status in the SOLUTION module for the converged solutions using
CNCHECK.
*** ERROR *** CP = 389.766 TIME= 14:27:20
*** MESSAGE CONTINUATION ---- DIAGNOSTIC INFORMATION ***
Rigid body motion can also occur when net section yielding has
occurred resulting in large displacements for small increments of load
or when buckling has occurred.You can plot the time history curve
for node 21249 in the UY direction to check for stiffness (slope of
the curve) approaching zero.
请高手赐教！问题可能与前面的帖子有重复，请斑竹不要删贴，谢谢
模型 这是四分之一模型 高手斑竹帮忙看看阿 我也碰到了这类问题，不知有哪位可以指点一下？ Z方向加约束了吗？
接触单元选择闭合初试间隙选项了吗？ The only selected contact pair is initially open.Rigid body motion
may occur in any portion of the model held in place solely by contact
elements.
肯可能是初始间隙太大
对于第二个问题 应该有自由度约束的，建议加内表面节点的周向约束
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