Non Linear Material

About the development of the FEM module/workbench.

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Klemmkeil
Posts: 19
Joined: Sun Apr 04, 2021 11:12 am

Non Linear Material

Postby Klemmkeil » Wed Jul 21, 2021 8:25 pm

Hello everyone,
actually i'm building some non linear simulations.
In the last days i got some mechanical data from some tests in the laboratory, so i would like to implement it in my simulation.
The simulation works, it didn't made any validation, but i looked into the results and unter PEEQ there is just zero.
I thought maybe my simulation is not correct. Am i rigth?
If yes, what did i have done wrong?
I changed the input-file according to the picture by hand.
Mesh is generated extern in Gmesh

Greetings Nic
Attachments
input.PNG
input.PNG (36.94 KiB) Viewed 296 times
Klemmkeil
Posts: 19
Joined: Sun Apr 04, 2021 11:12 am

Re: Non Linear Material

Postby Klemmkeil » Wed Jul 21, 2021 8:29 pm

I cannot upload my model because of a http-error :shock:
i cleared mesh and the size schould be ok.
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bernd
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Re: Non Linear Material

Postby bernd » Thu Jul 22, 2021 4:24 am

PEEQ stands for equivalent plastic strain. For linear material PEEQ will be zero in any case. You will get PEEQ strain only if you use non linear material. There is a non linear material example in the FreeCAD FEM examples GUI. This will have PEEQ strain.

cheers bernd
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bernd
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Re: Non Linear Material

Postby bernd » Thu Jul 22, 2021 4:25 am

BTW, which FreeCAD version do you use? For FreeCAD FEM you should use 0.20 dev version.

cheers bernd
Klemmkeil
Posts: 19
Joined: Sun Apr 04, 2021 11:12 am

Re: Non Linear Material

Postby Klemmkeil » Thu Jul 22, 2021 8:56 am

I downloaded FreeCAD 0.20 and run my simulation.
Same result, i think the PEEQ must be bigger than zero, because the stress is so big, i must have plastic strain.
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Histogramm.PNG
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bernd
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Re: Non Linear Material

Postby bernd » Thu Jul 22, 2021 9:31 am

In real world yes, but not in a FEM analysis. If you do not tell the FEM solver the material should stop to use a linear curve for stress strain it will continue to increase your stress to infinity. In FEM this is normal behaviour in singularity points.

https://www.comsol.com/blogs/singularit ... red-spots/
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bernd
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Re: Non Linear Material

Postby bernd » Thu Jul 22, 2021 9:34 am

Do you have added a non linear material to your analysis or not? I may missunderstand something ... If you have added a nonlinear material there should be PEEQ stress ...

Have you played with the non linear example for GUI examples? Does this work for you? HAve you changed parameter in this example? Does it still work?
Klemmkeil
Posts: 19
Joined: Sun Apr 04, 2021 11:12 am

Re: Non Linear Material

Postby Klemmkeil » Thu Jul 22, 2021 9:34 am

My Part seems to big for uploading, if somebody wants it, i could provide by another way.
Just give me some advice which way you prefer.
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Part.PNG
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upload.FCStd
(6.79 KiB) Downloaded 2 times
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bernd
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Re: Non Linear Material

Postby bernd » Thu Jul 22, 2021 9:39 am

the file you uploaded misses the mesh! You should not delete the mesh object but clear the mesh from the mesh object (right click on mesh object--> clear).

In this file is only a cube ...

screen.png
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Klemmkeil
Posts: 19
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Re: Non Linear Material

Postby Klemmkeil » Thu Jul 22, 2021 9:40 am

Hi Bernd,
i used a non linear material an edited it in the input-file, like shown in the picture above.
Was that the rigth way?