#1 2021-10-27 15:06:40

clancy70

Member

Registered: 2021-10-27

Posts: 5

Help with first problem

Hi,
I have tried to get a very simple problem solved in aster, I am not familiar with this software very much and followed the first tutorial for the portal frame, and now tried my own problem and want to see what I am doing wrong. The problem is a beam supported at two ends with a traction applied to one surface.

The problem I think is I am applying a boundary condition to a line, when this is a 3d problem, I may need to define a group or something I believe for this group of nodes, as aster is warning that there are 'edge elements' defined. So I think I need to say that this group of elements in Gmsh actually corresponds to nodes of the 3d elements, or something.

I have attached the problem anyway in case anyone has time to give me guidance.

Thanks

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Attachments:
beam.zip, Size: 14.15 KiB, Downloads: 109

jeanpierreaubry

Guru

From: nantes (france)

Registered: 2009-03-12

Posts: 3,776

Re: Help with first problem

hello

please introduce yourself in the relevant section of this forum

jean pierre aubry

---

consider reading my book
freely available here https://framabook.org/beginning-with-code_aster/

clancy70

Member

Registered: 2021-10-27

Posts: 5

Re: Help with first problem

Done!

filjan

Member

From: Poland, Cracow

Registered: 2016-07-11

Posts: 85

Re: Help with first problem

Hi,
I have tried to get a very simple problem solved in aster, I am not familiar with this software very much and followed the first tutorial for the portal frame, and now tried my own problem and want to see what I am doing wrong. The problem is a beam supported at two ends with a traction applied to one surface.

The problem I think is I am applying a boundary condition to a line, when this is a 3d problem, I may need to define a group or something I believe for this group of nodes, as aster is warning that there are 'edge elements' defined. So I think I need to say that this group of elements in Gmsh actually corresponds to nodes of the 3d elements, or something.

I have attached the problem anyway in case anyone has time to give me guidance.

Thanks

Hi!
You tried to impose force on beam-like element which is absent in your mesh - pointed group is another type i.e. faces of 3d elements. Probably you need FORCE_FACE keyword in AFFE_CHAR_MECA.
Regards
Filjan

jeanpierreaubry

Guru

From: nantes (france)

Registered: 2009-03-12

Posts: 3,776

Re: Help with first problem

hello

this is worse than filjan describen

the is very incomplete, among many things there is no volume defined
the .comm file is incomplete as well

i suggest you read chapter 12 in my book there is a similar volume defined and meshed, together with a command file

jean pierre aubry

---

consider reading my book
freely available here https://framabook.org/beginning-with-code_aster/

clancy70

Member

Registered: 2021-10-27

Posts: 5

Re: Help with first problem

Thanks for the suggestions.

I got something 'working' in the sense the solver does something and provides a displacement field to look at. I had mistaken FORCE_POUTRE for a general nodal force but the documentation corrected me on this and now I see it is for use with structural elements as mentioned. I did not realize a physical volume had to be defined as well for 3D problems.

I think now my strange results might have something to do with face normal orientations being wrong out of gmsh, so need to try something similar to what is in chapter 12 as you mention to correct them.

clancy70

Member

Registered: 2021-10-27

Posts: 5

Re: Help with first problem

All working as expected now, at least the displacement looks somewhat reasonable

filjan

Member

From: Poland, Cracow

Registered: 2016-07-11

Posts: 85

Re: Help with first problem

Consider practice with some essential examples from web and books like Thakore's guide https /www.amazon.com/Finite-Element-Analysis-Source-Software-ebook/dp/B07J9X769N

regards