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Working correct with shell properties

Good evening everybody,

i hope my question is understandable and someone can may help me.

I want to proof an analytical task with optistruct. On a thin beam are several forces attached and he has a thickness of 2mm. The force Fx and the moment Mz are charged on the hole surf, so i took the force as a pressure an spread the moment with a rbe3.

The main problem is, that i don´t know if i used the shell elements the right way. First i tried to work with a midsurface, but this doesn´t work at all. So i meshed all surfs with a thickness of 2.0 in properties. Is that correct?

And how can i get the pricipal stress in x direction in hyperview? I tried it with 'Element Stresses (2D & 3D)' - P3 Minor and mid layer, but i think that is not correct. The analytical result was 224 N/mm².

Sorry for this stupid questions, but it took me hours and hours and i didn´t made any progress.

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tinh

it is incorrect if you mesh all surfs

you should mesh on mid-surf. could you show us results in that case? why doesn't it work?

Beginner93

Hi,

thanks for your help.

I don't know how to fix the force Fx (like a pressure) and the moment Mz. Because with mid-surface there is just a line and no surf in x direction.

tinh

You can bind nodes by rbe3 then apply force and moment to the dependent nodes

Beginner93

Now i i´ve worked everywhere with rbe3 where necessary, but now an other error appears.

image.png.ca66c366f2988564f99b2f2ba6dfd7e8.png

In a second try i managed the problem in an other way. Now i fixed the rbe3 only the lines otherwise i got errors or the result is completly deformed. But this couldn´t be the result i think. The force should be attached to the whole surf and not just to some lines.

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tinh

I think at the alternative end, you bind nodes by RBE3 and constraint it's dependent node.

Please use RBE2 at that end

Altair Forum User

hi@Beginner93

Why don't you create 1D element and assign T-section for that and do the analysis.

Thank you

Beginner93

Thanks a lot for your usefull help.

@Premanand Suryavanshi but isn't there still the same problem that I have to mesh the midsurface and fix the loads on a line?

Altair Forum User

no for 1D you no need to extract mid surface.. please go through 1D learning course once. You will get clear idea.

Thank you

Altair Forum User

Please go through the below link for 1D tutorial.

https://certification.altairuniversity.com/course/view.php?id=71&section=3

Thank you

Altair Forum User

HI @Beginner93, @tinh

The image is not clear to me.

The top view section shows the load application is at the free end and at the section view it is on one end of the flange (the red round location)

If it is the latter case, 2D elements should work with RBE3 or RBE2.

If it is the first case, I think Beam T-section is sufficient.