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Element type for simulation - Solid or shell




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?




Re: Element type for simulation - Solid or shell




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.