Water tightness errors really bug me. Any easy way to solve these? 1

[laminarflow]

I have a tubular frame and half the time I get water tightness errors. What gives and is there any way to find and fix these in the Model? I am using Alibre and Algor Design Check.

 

[GBor]

Once upon a time, I heard that this was a precision issue...Algor was double precision and some CAD softwares were single precision, but I thought that was pretty much resolved these days.

I don't use Alibre, but are you using the Algor icon within Alibre to go from one to the other? If not, what format are you exporting?

 

[LOUDOG]

In my expirience Algor doesn't like to mesh structural frames unless you do really fine meshes. This usually results in ridiculusly large models. You should really model this in Algor using beam elements.

 

[laminarflow]

Hi, It has tubes connected together so it is more than just a truss. There are some tubes in bending with some plates, etc. I can get it to mesh correctly 1 out of 3 tries and the results at least make sense. If I get into more of this I guess I'll get a full version but for now I'll try to make do with Design Check.

 

[GBor]

I just had another thread where Design Check was mentioned. I'm not familiar with that level of package, but it sounds a great deal like Cosmos Express. If that is the case, put down the computer and step away!

Brick elements for tubes and plates will not give even remotely the correct answer. There is a reason why beam theory, plate theory, and brick theory are addressed differently in most software packages...the structures behave differently!

Bricks will be overly stiff in bending for both the beams and the plates. Don't know what your structure looks like, but I would question the results that you have been able to obtain unless you have been able to, at a minimum, control the element types and the mesh.

 

[mdekato]

I also use Alibre and DesignCheck. When I see the watertight problems there can be a couple of problems.
1) A small fillet or chamfer.
2) The transition of a radius or chamfer across two non-coplanar surfaces.

If you see where the watertight problems are it can speed you to a solution. The way to show them in DesignCheck is to go to (on the toolbar) View > Options > Layer Control. This pops up the Layer control dialog box, turn off all layers except Layer 2 (I think that's one) and the problem area will be bounded, along element borders, in red.

 

[rybose]

If you say you have a "frame" you should be using beam elements. Period.

I've tried to mesh a welded tubular frame with shell elements and wasted 3 weeks trying to get the meshing to work. It never did. In the end it was the wrong approach anyway.

I assume that when you say "tubes in bending with some plates" that there are some triangular gussets welded to the frame. If there are welded plates at the joints of the frame these can be modeled as plates attached directly to the beam elements.

A frame structure with gusseted plates is most easily modeled in ALGOR "by hand." It's really not as bad as it sounds, and will be a lot faster than fighting with the automatic meshing tools.

When you need higher fidelity results at the joints you can always make detailed 3-D submodeled using the internal forces from the beam element model.