Wing ribs, spars, etc

[Farhan Malik]

Does the current version of OpenVSP support modelling wing internal structures such as ribs, spars, etc.?

[Rob McDonald]

Yes, 3.14.1 and newer have an ability to model structure.
Unfortunately, we haven't had time to put together any documentation,
tutorials, or videos on it yet.

You access this capability from 'Analysis' 'FEA Mesh'.

You must first create a 'Structure' associated with a single Geom
surface's OML (Say a wing, or a fuselage).

A *.vsp3 file can have many Structures in it. There can be multiple
Structures associated with a single Geom (say main wing structure and
control surface structure).

With a Structure created and selected, you can then add 'Parts' to it.
There is already a 'Skin' part, but you can add ribs, spars, etc.

A material (steel, aluminum, etc) is associated with each part -- and
also properties (thickness, Ix,Iy for beams, etc).

The Mesh tab allows global curvature-based control of the mesh resolution.

The Display tab allows you to control what you see after a mesh has
been created.

Click the 'Mesh and Export' button at the bottom to make it go!

Start with something simple and get the hang of it.

Rob

On Sun, Dec 17, 2017 at 10:39 AM, Farhan Malik <far...@mac.com> wrote:
> Does the current version of OpenVSP support modelling wing internal
> structures such as ribs, spars, etc.?
>

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[Justin Gravett]

Like Rob said, we're working on getting a tutorial video out as soon as we can. However, there currently is a wiki page with documentation for the tool available here: http://www.openvsp.org/wiki/doku.php?id=feamesh.

-Justin

[Bryan Sandoz]

Hello,

I have been trying to use this, but am getting stuck at the very first step.  When adding a "slice" part, I am unable to find a dialog where I can adjust the location of the slice? 

Thanks,

Bryan

> email to ope...@googlegroups.com.

[Rob McDonald]

Under the 'Add Part' button there is an 'Edit Part' button that appears when you choose a part.

Rob

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[Bryan Sandoz]

Ahh, thank you, sorry to bug you with a simple question!

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[Kevin Gnanaraj]

Sorry to resurrect an old thread, but is there any way to model ribs and spars without the FEA? The FEA crashes when using ribs and spars, and I'm using ANSYS to do a static structural analysis right now, and I want to get the ribs and spars in the STP file that is imported.

This is for a simple wing, no dihedral or twist, just 2 sections with a taper on the outboard section.

[skyc...@gmail.com]

Hi Kevin,

No worries!  There is a way to export the untrimmed structures via File -> Export and selecting Untrimmed STEP Struct or Untrimmed IGES Struct.  Unfortunately, I haven't been able to get the untrimmed STEP or IGES exports to work recently.  Rob mentioned briefly to me that there might be some ability to fix that in the future.  

Regarding the crashing that you're seeing, I'm getting some similar results with a very similar wing.  I too am working on a 2-section wing with a taper in the outer section.  If the FEA is straight crashing you might try setting a smaller min edge length, as it seems to crash on me if I've set that larger than a specific feature (be careful of thick trailing edges, you'll need a min edge length smaller than the smallest trailing edge thickness or better yet go into the wing component definition and under Modify set Trailing edge closure to something like skew both to remove the thick trailing edge.)

There is a slightly different problem once you get it to mesh, the spars themselves if you've limited them to specific sections, they kind of "overcut" into the next section.  If the spars are angled from each other a fair bit (think a Cessna 172 main wing aft spar) then it's not a big deal but add extra "spar" elements.  If the spar sections are almost in line with each other at the same x/c, it can create intense sliver elements, some of which might cause VSP to crash (maybe, I haven't really seen it, more I run into those issues later when running a FEM).   Using the "Trim to Bounding Box" option will produce different results that may be more or less desirable.  Having it off prevents the wing from overshooting into the next section, but sometimes produces spurious spars which are not connected to the skin, etc.  This is with 3.32 or 3.34 right now.  I think we'll have some fixes for this in the queue here at some point.  

Thanks,

Bryan

[skyc...@gmail.com]

I spoke too soon!  I was just able to export an untrimmed structures STEP that was readable by Solidworks.  Same with the untrimmed STEP. 

[skyc...@gmail.com]

You will still have to trim everything in Ansys manually though.  

[Kevin Gnanaraj]

Thanks Bryan! With your suggestions I was able to get a mesh, and the untrimmed struct file. I wasn't sure what that was before, but now I do. I think I'll still mesh in ANSYS for now, since that has better options.

[Kevin Gnanaraj]

I'm seeing the scale being reset when using untrimmed struct STP files. Are you having this issue too Bryan?

When I import these files into Ansys or Solidworks, a 20 m wing becomes 0.02 m. I can rescale it, but it's a step that should be unnecessary, since the non-struct files don't have this problem.