FEMAP layers vs groups

[stressengineer26]

Hi All,


I am trying to understand the difference between using layers and groups. I guess I do understand how they differ e.g. multiple layers can be displayed at a given time vs only one group can be visible at a given time. Also, a layer can only have one entity vs group can have as many entities. From your guys' experience, could you please answer the following. This will really help me nail the conept! thanks in advance

1) why will somebody prefer to use a layer and not a group
2) while in a visible layer, if you make change to an entity, will that update the original model?
3) while in an active group, if you make any changes, will that update the original model? Can we have it such that it doesn't update the original model?

Any other pertinent info you guys think will help will be highly appreciated.

Thanks again guys.

 

[APav]

Hi,

I'm not a layer user but here a few tips:
1) multiple groups can be displayed, starting from FEMAP v10.3 or so developpers added the "Show Multiple Groups" capacity
2) I don't get "a layer can only have one entity vs group can have as many entities". Layers have a smany entities as you want.

3) on a more general level: layers are just that: they are thought out to be "layers" of your model. So for instance imagine a box within a box within a box...etc. each box would be a layer, making it easy for the user to "dive into" the FEM layer after layer.
Following that idea Layers are mutually exclusive: an entity can only belong to ONE layer. Also Layers are complete: all entities in your FEM are contained in one (and only one) layer.

Groups are more open: an entity can be in several groups, and your entire FEM has no reason to be "properly" organised into groups.
However as versions went by, a few more functionnalities have oriented the user towards groups. First off you have an entire menu of functions associated with groups. Then for NASTRAN users, groups are very much like sets: they are lists of IDs, it's then up to the user to know what to do with them.

Now for you updating questions: groups or layers are not sub-models, so any update WILL change the original model. However you can easily export a group (right click on it, "Export Neutral", and reopen it, that is if it is "self sufficient". So for instance if you have nodes which reference a coordinate system, that system must be in the group to be exported. The easy way to make sure of that is to right click the group and use "Add related entities". This will expand your graoup so that it is self-sufficient.
Once you have the group neutral file, you can open that one in FEMAP and this time any modification will not change your original models, because this time FEMAP sees these models as completely apart.

This leads to the subject of "includes" (if you are a NASTRAN user). Sub parts in your model can be organised in the dat file using the include statement. Upon import FEMAP can automatically create fgroups for each include statement. Then when modifying one group (ie one include file), all you need to do is export only the concerned group, and the rest of your FEM does not change. I don't know if this is what you're trying to achieve.

AP

 

[rb1957]

3) I understand changes to the model are real time ... you can't change a group in isolation (a group is only part of the model), you're not changing the group data, you're changing the model data.

if you want to retain the original model data, save the changed model with a different name. I find the "notes" tab as a good place to record changes in the model.

another day in paradise, or is paradise one day closer ?

 

[ThomasH]

Hi

For me is is not a question of using Layers or Groups, I use both simultainously. But with different purposes due to their different properties.

If you have an object, any object, it can only be in one layer but it can be in any number of groups. The "old" limitation that you could only show a single group but several layers no longer applies. Now you can show multiple groups and actually use bolean algebra on the groups.

But to illustrate one method to work with layers and groups.

Imaginwe you shall model a building. You have severel floors and each floor has to load carrying systems. Horisontally you have beams and slabs, vertically you have walls and columns. And a beam on the third floor has no reason to be in any other layer than 3rd floor beams/slabs. So you have two logical layers for each floor. And if the building has different parts you can sprit them into diffenet layer number series.

And in this manner you can organize huge models based on dividing the logical parts into layers. And now the limitation that an object can only be in one layer may actually be an advandage. There is no risk that any beam exists in two layers. It can be in the wrong layer but once it is in the correct layer, that is final.

Now, one thing with the groups is that you can use a group to vizualize results while postprocessing.

Say that you have three types of beams in the slab/beam - system. Using the layers to show the beams on a specific floor and the group to vizualize the moment values in a specific beam type you can show the results very clearly. And since you can group properties or materiels directly in the model info three (right click) it is very fast.

This is one example of a way to use layers and groups. Since they have different properties I think the trick is to find a way to use the "limitations" as a strengt. But I usually use both of them together.

As for your other questions regarding updating, I think they have already been explainen.

Good Luck

Thomas