cmas2d.gid question

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mte111
Posts: 2
Joined: Mon Jun 14, 2021 1:52 pm

cmas2d.gid question

Post by mte111 »

Hello,

I'm looking at the example, cmas2d.gid, as an early step in learning about GiD. It is all pretty straight forward but I'm not seeing any mention of where or how one assigns material properties (in this case density) to the various elements. In this example all the elements have the same material property so It isn't that big of a deal but say there were different volumes, surfaces, whatever in the model that have different properties. First, it looks like the different entities sort of lose their identity in the mesh and secondly how does one go about assigning the appropriate material properties to the various mesh elements and knowing which mesh element corresponds to which mesh entity?

Thanks.
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escolano
Posts: 1915
Joined: Sun Sep 05, 1982 10:51 pm

Re: cmas2d.gid question

Post by escolano »

Maybe I don't understand well your question.
In the cmas2d.gid (classic problemtype) as user you must assign a material to each geometry surface. (each entity can have 1 and only 1 material)
Data->Materials... Assign->Surfaces
when generating the mesh all elements of each surface will inherit the material from its surface.
It is unrecommended in GiD to directly assign properties like material directly to mesh elements, because this assignation will be lost if do you re-mesh.

If do you need more than one material assigned you must before divide the geometry to have the appropriated surfaces for your different regions.

Nowadays, after mesh, the elements don't have any link to its geometric entity. Usually It doesn't matter. (for the simulation input usually the only that matter is the mesh, not the geometry)
There are special tricks if exceptionally do you need to know for an element the entity id of its source geometry (e.g. assign an extra condition with a special #FUNC#(NumEntity) field

In future GiD developer versions maybe we will store nativelly this extra links from mesh entities to geometry entities, but it require extra memory resources and an overhead in some operations.
mte111
Posts: 2
Joined: Mon Jun 14, 2021 1:52 pm

Re: cmas2d.gid question

Post by mte111 »

Thank you, Escolano. You answered my question. The document/description of the cmas2d.gid example didn't mention assignment of materials to entities anywhere. It did mention defining the materials but no mention of making assignments, hence my question.
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