Dear all I have a 3D model with

[FSB1]

Dear all

I have a 3D model with CTETRA solid elements and I need to get the maximum force in the structure when running a static analysis.

The problem is when I request force (FORCE=ALL) I don't get any force output... why?

 

[ThomasH]

Hi
I seldom work with solid (3d) elements but don't they usually give results as stresses, not forces?

Thomas

 

[FSB1]

Hi

yes they give stress results, but what about the forces? if the stress result is available, there should be forces somehow...

 

[ThomasH]

Hi
What would the forces be based on?

For 3d you have force/area = stress.

Thomas

 

[ThomasH]

Hi again
You can perhaps consider it this way. For 1d and 2d elements you have area or thickness as input. That means that the solver can multiply the stress to get either force or force/length. But for 3d elements there is no parameter to multibly the stress with for the solver.

I don't know exactly what you want bu freebodys may be an option depending on the postprocessor.

Thomas

 

[FSB1]

Hi

I have a 3D model and I want to know the maximum force present, under certain load conditions

maybe solid elements are not the best to get the maximum force?

With shell elements for a plate for example, I can get the forces, but now I have a more complex geometry and not easy to model with shell elements

 

[marulanda]

GPFORCE = ALL, you will have the force on all nodes, but I don't konow why you know want this info on 3d elements, is completely needless

 

[aerostress82]

If you had a perfectly constant size and quality mesh (if your current tet size is 10mm, you could achieve this perfection with 1mm elements), this type of FEA model would give you the maximum "force" element as the maximum "stress" element. It is a little sci-fi, but it the only way you can achieve this.

Or you can check freebody loads with GPFORCE = ALL as marulanda mentioned in this perfect mesh model. Again you would "exactly detect" where your biggest "force" in the model would be.

If you can't do sci-fi stuff due to CPU or budget constraints, second degree tet elements are mostly accurate enough for the peak stress checks as long as they are modeled as 2-3 or more layers of mesh along any thickness throughout the model. You could also try this instead.

Spaceship!!
Aerospace Engineer, M.Sc. / Aircraft Stress Engineer

 

[FSB1]

Hi guys, thanks for your help