Impose displacement on only one node of the FEM mesh
Impose displacement on only one node of the FEM mesh
(OP)
Hi experts,
I am experimenting with a FEM package and try to solve a very simple static linear problem :
Take a sphere made up of solid linear isotropic elastic material. Impose :
- zero displacement on the boundary of the sphere and
- arbitrary displacement to the node located at the center of the sphere (the mesh was generated to ensure there is one node there).
In order to minimize the energy of deformation, I would expect that the displacement imposed at the sphere centre would be smoothly damped to zero at the boundary of the sphere.
Instead of that I observe that the displacement is abruptly damped on the first couple of cells surrounding the center point, whatever the mesh refinement. This leads to inverted mesh.
I have the feeling the solver used is not robust enough to deal with such one-point constraint. Any idea or suggestions for improvement ?
Thanks
Sylvain
I am experimenting with a FEM package and try to solve a very simple static linear problem :
Take a sphere made up of solid linear isotropic elastic material. Impose :
- zero displacement on the boundary of the sphere and
- arbitrary displacement to the node located at the center of the sphere (the mesh was generated to ensure there is one node there).
In order to minimize the energy of deformation, I would expect that the displacement imposed at the sphere centre would be smoothly damped to zero at the boundary of the sphere.
Instead of that I observe that the displacement is abruptly damped on the first couple of cells surrounding the center point, whatever the mesh refinement. This leads to inverted mesh.
I have the feeling the solver used is not robust enough to deal with such one-point constraint. Any idea or suggestions for improvement ?
Thanks
Sylvain





RE: Impose displacement on only one node of the FEM mesh
www.Roshaz.com
RE: Impose displacement on only one node of the FEM mesh
It seems to me that the problem is well posed even though the situation would be difficult to experiment. Maybe you can imagine of piece of rubber molded around a small magnet that you put in a strong magnetic field, while holding the surface.
RE: Impose displacement on only one node of the FEM mesh
You cannot expect any FE software to give you meaningful results.
You could perhaps create a small spherical void at the centre and apply a pressure to the void surface. Be sure to put sufficient elements on the void surface.
www.Roshaz.com
RE: Impose displacement on only one node of the FEM mesh
I also see that using an elastic-plastic material can also help going around the problem. I'll see if I can improve that, or if the whole thing is just a bad idea.
RE: Impose displacement on only one node of the FEM mesh
Brian
www.espcomposites.com
RE: Impose displacement on only one node of the FEM mesh
if it is, then the nodes adjacent to the displacement will react the load, and most of the sphere will be doing nothing.