Non adequation between 2D and 3D representation

Altair Forum User

Hi all,

 

I am working on an analytical problem of a circular plate under distributed loading conditions, and with all edge nodes constrained. 

I first modelled the plate with 2D quad elements, thickness 0,35mm.

Then I modelled it with 3D brick elements, thickness 0,35mm (8 elements in the thickness).

 

Of course I would like to find the same order of magnitude concerning both results. But I do not in terms of deflection. 

Does anyone has an answer to this ? 

 

Thank you in advance,

Alice

 

 

Altair Forum User

Hi Alice,

Normally it should give the same results. Only for the deflection you are getting a different result?.

Please see this link http://www.altairuniversity.com/wp-content/uploads/2014/02/meshing.pdf (Page No:5) where a similar case is done.

Altair Forum User

Hi George,

 

I get 1mm deflection with shells, 7.10-2mm with Bricks. 

The other parameter I check is the resultant force on the clamped edge, to be the sum of all nodes' loads. This is ok, but the deflection not...

 

2D plate:

- clamped nodes at edge

- all innner nodes under loading

 

3D plate:

- clamped nodes at edge on all layers (8 elements in thickness)

- all inner nodes on upper face under loading

 

 

Q.Nguyen-Dai

Share your model?

Altair Forum User

here you go,

thank you

Unable to find an attachment - read this blog

Altair Forum User

I try changing the properties /PROP/SOLID from Isolid = 17 to 14, as 14 is the default value for IMPLICIT option, I am using. I put Inpts to 222 and I get a deeper deflection but showing weird localisation (see attached picture, highly zoomed in to see the problem). It is as if I did not apply the load in the center, but I apply the same load as before, when I used Isolid = 17.

 

I read about the HA8 and H8C elements properties but do not understand how I can come to such wierd results on displacement. Could you explain me the differences between these 2 options ? 

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Hi Alice,

Will update you on this regard very soon.

 

Altair Forum User

Thank you George, I checked everything again, and do not understand what is wrong.

Altair Forum User

Hi Alice,

This seems strange. 

Normally it should give similar results. Did you try with different element formulations?.

Also, as a workaround can you try with second order solid elements?.

 

 

Altair Forum User

I tried with second order BRIC20 elements as you suggested. Viewing is even worse (see attached file)...

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Hi Alice,

Please share this specific model starter and engine file.

Altair Forum User

Thanks in advance

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