Element Deformation Only Error

[ultiweapon]

Hello,
I'm fairly new to ABAQUS and Finite Element. I have an issue which has been occurring multiple times and I need help on this. I have a cantilever beam which is applied with pressure load at the end of the beam on the top flange
but the only thing that deforms is the element (as shown in the attachment).

When displacement is applied instead, elements at the points where the displacement is applied
deforms in a similar fashion. I'm expecting that the whole model works as a "system" not "local"
to the connecting elements. It deforms correctly sometimes (as a system) but often turns out like this.
If it helps, element is a C3D8. Beam is connected to a column with modeled 3d bolts.

Anyone can offer any advice on why is it happening?

 

[mturkol]

Hi,

I do not know the details on how you apply that pressure, BC's and how mesh-sensitive your problem is; but your problem might be mesh sensitive. After making sure that you sort out the correct BC's and the distribution of the pressure, check that you have a mesh fine-enough. As a general practice, solid elements are not good at modeling bending behavior compared to beam or shell elements. But since you are working on a problem that includes 3D bolt models, I would also make sure you are applying the correct pressure distribution by applying statically equivalent nodal loads. Someone very recently asked a question on this in this forum and I provided two pictures that explain how to do it. You can take a look at those.

Again, I do not know every detail on how you implemented the ideas on your FE model. So, you might need to be careful on how you are trying to make the model work.

 

[ultiweapon]

Hi mturkol,

Thanks for your reply.
Pressure is applied over an area, being:-
Loads -> Pressure -> Select faces
Pressure has been set to Uniform & Ramp.
I believe that this would be equivalent to
the method that you've shown. Thanks.

But your response made me think, perhaps I would
tinker around with the BC's and report back.
I remember now someone told me that the FIXED support
has issues with brick elements. Can you verify this claim?

Thanks.

 

[mturkol]

I did not work with brick elements. Try first working on a simpler problem by modeling the beam with beam elements, using fixed BC at the supported end while applying that pressure on the free end. There might be an issue with your BC's, or your bolted connection representation in your FE model. Your result did not seem realistic to me. I would always recommend attacking a more detailed problem by first seeing a general response from a simpler model. Then you can move on to more complicated models including more detail. Bending behavior for a beam could easily be simulated using beam elements, so see if what you get from that simulation is satisfactory. There are should be an analytic solution to your problem for your frame problem. Compare with that.

 

[akabarten]

Hi,

Check does your system unit (material data and load units) is consistent.

Regards,
Bartosz

 

[corus]

Given that the deformation scale factor is 1, and there appears to be no stress at the applied load position, it seems to show that you have a more fundamental problem with the model, and nothing to do with mesh sensitivity or units. You must have contact conditions imposed with bolts so I'd check if your mesh is connected, and if you've applied contact conditions in the right place.

 

[ultiweapon]

Thanks for the responses.

@mturkol - Yes, I could try that but I think I have one last trial to check just to see the difference.
@akarbaten - Checked the units. Seems fine and consistent.
@corus - The thing is that it works sometimes? So the contacts doesn't seem to be a problem though.

I have a hunch that it could be the FIXED end supports with solid elements.
Going to run it tonight and I will report back here if it fixes the problem with this same model.
If it does, then it definitely shows that the FIXED support is the culprit.

 

[IceBreakerSours]

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