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Element type for simulation - Solid or shell

Pioneer
Pioneer

Hello,

 

Refer to the attached image extracts from CAD and Femap. My typical approach to simulate such models is to import the solid objects into Femap using *.sat format and then mesh with solid finite elements with midside nodes (priority is to have a hex mesh for all objects; if some objects cannot be hex meshed using simple Femap options then I go for tet mesh).

 

I have the following three queries-

  1. How can I make sure that the solid element locking phenomenon doesn't occur?
  2. I read something about solid-shell finite elements in which EAS or ANS methods are used to remove locking. Does Femap offer such options?
  3. Is there a thumb rule to decide whether to use solid elements or shell elements?

Regards,

Su

2 REPLIES 2

Re: Element type for simulation - Solid or shell

Creator
Creator

Hi!

 

If I had a structure like this I would do the following:

  1. Slice the structure into a upper part and the base plate
  2. Create mid-surfaces of the upper part
  3. Take the upper surface of the base plate as an additional surface and do a non-manifold add of it together with the mid-surfaces.
  4. Mesh all those surfaces.
  5. Extrude the elements of the top surface of the base plate to get hex or wedge elements, discard of course the source elements.

Re: Element type for simulation - Solid or shell

Gears Phenom Gears Phenom
Gears Phenom

1. Are you talking about volumetric locking? AFAIK this phenomena occurs in incompressible materials, with Poisson`s ratio 0,5 like rubber. Not steel or other metals/ceramics/concrete.

2. This is basics of structural mechanics, not FEA.

Two dimensions less than third -> beam.

One dimension less than two others -> shell.

All dimension are equal -> solid.

However, all depends from task - what you want to calculate. If you want estimate global stiffness - use plate. If you study some small part of your structure (for example in scientific/research problem), then use submodeling - plates and solids in zone of interest.

So now you have two votes for shell model and zero for solid model.

95% of structures can be properly solved with beams and shells (ships, planes, cars, buildings, bridges etc.).

It is not common practice to mesh every structure with solids. I see people who mesh beam with 0,5M tetra to get beam deflection from point load.