MegaSack DRAW - This year's winner is user - rgwb
We will be in touch
Hi,
I'm just about to hand-in my Y3 final design project. During it's course I experimented with a little FEA to improve the design [reduce stress] but I am having trouble with my solid model.
When I first drew it I added rounds to better model the finish that a rotomould part would have. In my mind these rounds would significantly reduce stress concentrations, so they would make a difference to the behaviour of the structure and I put them in.
The problem is that in Solid Edge I cannot correctly delete the rounds, as they have interacted with one another. The upshot of this is that while I am able to make the proposed changes to my design to reduce stress, I cannot run the resulting model through FEA as the remaining small parts of rounds cause the FEA to fail. I had to delete some rounds to make the changes.
Is anyone more skillful at this than me willing to open the part and use a clever trick they know to fix the glitches then send it back so I can run the FEA and verify my improvements?
I would of course fully disclose this in my report, I will not be passing the fix off as my own.
Alternatively, if anyone is really skilled with Solid Edge, perhaps you can help me to fix it? I tried using the part diagnostics and various export/import combinations [which has worked before], and I've even rebuilt a few surfaces manually, but it's just not working.
This
[IMG] 
[/IMG]
should take 20 minutes, but I'm about to give-up now. I tried a coarser mesh but the small slivers crashed it.
Thanks
Sam/GfS
Evening bump
I can help. Email is username at hotmail.
When you say "rounds", I take it you mean "Fillets" or "Rads"...?
Can you save the model as an Inventor ".ipt" ?
(Or a ".step")...
(Although Inventor might open a solid-edge part, I've not checked before).
If I can get a Licence over my remote log-on, I can take a look but it will be much later when the kids are in bed...
😐
Cheers guys - I'll send the .par and .stp to toys19 as soon as I've finished the part I'm working on. If he's not able to fix it I'll send it to takisawa2.
In SE there's "Chamfers" and "Rounds", I'm sure they're all the same thing.
Thanks!
you should be able to export x_t too, try that.
If I was at work I could help, but, there may be a way to control the meshing where the fillets are. I'm guessing the default mesh size doesn't like the small rads.
I'd take the rads out completely. If the design is so close to failing the rads help, I'd say re-design it.
Toys - Just sending an email.
Rich, I think you're about right, but it's not the rounds that make it strong enough, I just foolishly wanted to include them for completeness, but now they've buggered the modelling. 🙁
I think it's just a case of knowing what you're doing, and I'm the only guy using SE, or doing sims, so I am kinda out of options for help around here 🙂
Maybe someone more 1337 can fix it easily?
Sounds like you modelled in Solid Edge, and the reason you can't undo or suppress the edge blends is that you used synchronous modelling rather than history based?
It's always tempting to put the fillets and rads in sooner rather than later, but it's normally best to leave them as late as possible. Obviously, sometimes you need them for other features, but they add complexity to the model which you don't need until the end.
Hmm, yes. We were taught Ordered, but on placement I started using Synchronous. I thought the one was a replacement for the other, certainly being able to modify things on the fly is great, but it does tie itself in knots.
Is there a good online course for SE ST6? Beyond the tutorials I mean. I need to be shit-hot at it next year for my Masters!
Thanks Rich, I'll remember that.
My comments were based on historical,(=ordered?). I use Solidworks so may not be totally applicable to Solid Edge.
I cant fix it in keycreator on the stp you sent me.
the geom is filthy.
you need to recreate this from scratch and do fea on a simpler geom.
What the hell are you all talking about?!
I can have a quick look if you send me a step & solid edge file. From the above comments it may not be possible though. andy at williams dash net dot co dot uk
Gosh that's weird. I don't understand how these things can happen, you can add features but you can't delete them properly afterwards? I guess there is a reason to do with the intersecting rounds, I'll take richmars' advice and not use rounding 'till the last steps. Another friend of mine was grumbling about using SE as a preprocessor, maybe it's just not good for this?
Any tips about where I can learn more about how to do it better in the future?
For the other Rich:
He's saying the model is full of faults or discontinuities.
FEA is simplification of a solid object model [which contains effectively an infinite number of bonds and connections between molecules] to a finite number of connections with known behaviour [f=kx etc]. This allows Finite number of elements to be analysed, a simulation run to determine the behaviour the connections between them, and thus derive a useful model of the behaviour of the object subjected to loads.
Basically, computer structural analysis of a solid model.
Breaks/gaps, or self-intersecting surfaces will cause problems with the analysis, and because I've added blended rounds to the right-angle edges, and then deleted them, it's buggered up.
Thanks Andy - I'll bung you the files. Cheers for the offer.
This place is full of most excellent people...
Cheers Sam, that nearly makes sense, to me!
Sometimes these things are limited by the mesh I use nastran and nx which are the bigger brother to St however learning which type of mesh to use when and where is an experience thing
Sometimes tet mesh will try to place nodes ontop of points and this is just not going to work ,nearly all solid modellers are actually just automating surfacing tasks (eg extruding capping and stitching) in the background and its not unknown to have surfaces on surfaces with one that is unstitched we used to get around this by deleting a face checking the integrity of everything else then re capping it.
Inventor used to show erroneous stress in radii under certain conditions which you know in reality would be false
gofasterstripes - did you have any luck with fixing your model, or improving the mesh?
Oh hello!
Sorry guys I was busy busy busy busy and didn't see this. Still am, kinda.
I didn't manage to make it work, sadly. I think I have learned a lesson about not adding small features 'till the very end.
Andrew had a valiant attempt but it seems it was irreparably buggered.
No worries though, I did the very best with what I had and handed it all in. Just a waiting game now.
My girlfriend thinks I did well though 😉
[IMG] 
[/IMG]
[IMG] 
[/IMG]
[IMG] 
[/IMG]
Time to make a design show poster and rock out 🙂