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mansin

Symmetry with RBE3 element

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Hi,

I have a problem with planar symmetry on a tube. One end of this tube is full constrained, the distributed force on the other end is applied by the concentrate force (or torque) on dependent node of RBE3 element. To reduce the model, a quarter of this tube is constructed. For the nodes on symmetry plane (X-plane and Y-plane) except the dependent node of RBE3 element, the (156 and 246)DOFs of these nodes are constrained. The model is shown as follow: (Fz=1000, Tz=2000)

 image.png.937e1b55a51655ba6beca8a46d02087f.pngimage.png.a26c308b3f79a1b925972bcefaadb3a7.pngimage.png.33eb4293c52b5cb10303485d739308ae.png

However, the results of the two loads are not reasonable and right.

image.png.2be12d4820ee5d202f5defa919fb69d4.pngimage.png.48fc7ff4c449f17cdcfa7173f7d37437.png

I think the reason is the symmetry constraint of RBE3 element is not setup correctly. How to fix it?

I attach the results of the whole model (Radius=20, length=200, Thickness=2, Fz=4000, Tz=8000):

image.png.d4ad1de09ac229b4e78dd24bb89212e4.pngimage.png.c8b844599d0e47de697cf54a31247a43.png

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In force case, rbe3 must have 'calculated' dependent node (not tube center). This is planar symmetry.

 

In torque case, maybe PERBC will help. This is cyclic symmetry.

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In force case, I found that, even though using calculated dependent node with RBE3 element, the concentrated force cannot be distributed equally to all nodes of the truncated model. However, when I use the distributed nodal force directly and planar symmetry constraints, the results are equivalent to those of the whole model.

In torque case, I tried to use PERBC bulk data to simulate the cyclic symmetry, but I don't get any satisfied results. Doesn't the RBE3 element located in symmetry plane or center suitable for  symmetry constraint s?

F_Tq_on_tube_Quarter-PERBC.fem

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