FEMAP beginner STEP import 1

[LeonhardEuler]

Hello,

I am trying to analyze a FEMAP model with somewhat uniqe geometry. When I make my model in my modeling program I make an object as all one solid, but when I bring the .stp file into FEMAP it makes the object into 50 solids, or so. Why is this and how can I avoid this so the analysis is more manageable? I am getting many connection errors trying to connect all of these solids with auto connect?

Also I have a cylindrical object in this assembly and meshing it has proved to be near impossible for some reason with the mesh solid command and the default mesh sizes.

Thanks for any help.

https://drive.google.com/open?id=1KLbDVjkCkUXpM9bUa--LQixzdmzLNSta

link to model

p.s. can anyone give me a reference to learn how to make a contact simulation when objects aren't touching at first, but will be after force is applied.

 

[ThomasH]

Hi
I checked your model and it is unique, as is most models I work with. But it is by no means anyting extrem about it.

But from your description I am not sure that you understand how Femap works. Femap gives you great control over the model, but to some extemt you also have to take the control .
I don't want to be rude but my impression is that you use Femap as you would use the solver integrated in a software like Solidworks.

When you say cylindcrical object I assume that you mean the solid that is four pipes connected together. The pipes have a wall thickness of 0.15, default mesh size seems to be approx 1.1.
How do you fit elements with size 1.1 into a wall with thickness 0.15? The simple answer is of course that you don't, at least not with a good mesh.
If I instead give the default size to 0.15 (wall thickness) I get a reasonable mesh. But the model becomes huge in terms of nodes.

But what I don't understand here is why model this using solids, why not plates?

Your main issue may be the stffened plate on top of the RHS beam. That part is not imported as a solid, it's a bunch of surfaces. If you work with plates instead of solids it does not matter. Otherwise you need to fix it, probably easier in the design software. But it can be done in Femap.
For a plate model you can create a surface for the web and a small flange.

Contact, you mentioned that that "Auto" did not work.
As I understand this you have fairly easily identifiable contact pairs, set them up manually. If you use the auto-function the solver will check every possible contact situation, you dont want that, it takes time.

If I look at that parts I meshed (quick and dirty) there is a few million grid points. I have not meshed the stiffened plate so add another million or two. It can easily be reduced but I have not tried. Contact means non-linear, this can take some time to solve.

I would strongly recommend using a "plate approach" instead.

Thomas

 

[LeonhardEuler]

I am importing as a .stp file from inventor. Do you know how to import the model as plates instead of solids?

That plate is definitely my main issue and I don't understand why it is coming in as surfaces instead of one big solid, because that is how it is modeled. The only thing I can think is that the top "sheet" of the shape is too thin and FEMAP is not recognizing it as a part of a solid to connect all of the individual ribs.

Thank you for your help.

 

[ThomasH]

I would use geometry you already have in Femap as a base and build a surface based model.

Make a cross section of the RHS beam with lines, extrude them and you have the surfaces. Or use the midsurface functionality in Femap.

I don't think Inventor will help you solve this but I don't work with Inventor. To model that plate as a solid in Femap would not be impossible either. But I think it is the wrong method.

Thomas

 

[ThomasH]

Hi
How has things worked out for you?

Thomas