# SolidWorks FEA questions



## jucasan (Mar 18, 2012)

I just started experimenting with FEA in solidworks and I don't really have any experience in frames design. But here we are.

Just made this "testing" frame.
https://i850.photobucket.com/albums/ab61/jucasan/frame.jpg

This is where is restrained
https://i850.photobucket.com/albums/ab61/jucasan/restrains.jpg

and the load of 160lb.
https://i850.photobucket.com/albums/ab61/jucasan/load.jpg

and this is the displacement distribution.
https://i850.photobucket.com/albums/ab61/jucasan/displacementdistribution.jpg

The material is 6061 T6.

Is this something normal or I'm doing everything wrong?
Tx.


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## back40 (Apr 15, 2006)

Getting real world results out of FEA in not easy. Coming up with correct loads and restraints with the correct degrees of freedom is complicated. It's fun to play with but won't really tell you much without a lot of work. The distortion in your image is exaggerated. There is a setting for this in SW. It's much more useful to look at the stress plot that the actual distortion.


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## jucasan (Mar 18, 2012)

Thanks Back40 for your post. I agree with you that getting real world results is imposible. No matter how much knowledge you have, there are always loads, vibrations and all kind of behavior that we don't even know they exist. I'm just trying to lear a bit about this and hopefully in a few years be able do come out with something close to real world. So if anybody here know something, I'll be happy to know about it.


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## unterhausen (Sep 28, 2008)

it took me a while for "displacement distribution" to sink in. I don't think it tells you what you want to know, look at the stress distribution. The problem with the displacement distribution is that it isn't telling you what is in compression or tension


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## mrbigisbudgood (Apr 4, 2011)

It takes years to master FEA simulations. I've been doing it for 10 years and still, I learn every time I set up and run a simulation. That said......

I only use FEA at work to identify weak points in designs, "hot spots" if you will. It definitely helps drive your design in the early stages and can save time/money down the road by minimizing the failure/redesign/prototype/test/repeat cycle. But like you said...real world results are hard to come buy, and with the dynamic loads of a bicycle, damn near impossible.

Keep playing. Turn options on and off. Have fun. Nerd out.


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## bholwell (Oct 17, 2007)

jucasa said:


> this something normal or I'm doing everything wrong?
> Tx.


I would say that yes, there are a few things you could do to get more realistic results. The rear pivot should be constrained from moving in the x and y direction, but should be free to rotate. The headtube should also be constrained where the headset presses in. The load should be applied using a few different scenarios: a) all at the bottom bracket, b) all at the seat tube and steerer tube, and c) a combination of a and b.

I'm not sure that all of this is possible with the free version of Cosmos that's available with SolidWorks, though. BTW, what are you trying to determine with your analysis?


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## bholwell (Oct 17, 2007)

Oh, and you can't neglect the rear shock mount and upper pivot in the analysis of a FS frame.


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## jgrano (Dec 5, 2011)

How thick are your walls? 

I think it took my senior design group about 3 months to come up with our loading scenarios.. That being said our professor also does all the graduate level FEA courses so he might have just been a bit cruel. I'd try and find some more distributed loads basted on seat height and handlebar width. You can make these pretty easily just find the moment/force to apply at the joint. Might shed some more light on your results.


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## zac102 (Jul 24, 2010)

bholwell said:


> Oh, and you can't neglect the rear shock mount and upper pivot in the analysis of a FS frame.


That was the first thing I noticed. You don't have to use a deformable suspension within the FEA, but you could either have the linkage in the simulation as a rigid body (some FEA codes allow for this, not sure about COSMOS inside solidworks) or quickly run through a FBD to figure out what the suspension loads should be.

The other important question would be, "what exactly are you trying to do?" In general FEA (at least for linear and isotropic materials...) will do a good job calculating how a structure will react to the loading you give it. The trick is that the loading applied in the simulation needs to be the same as the lab test. It should also, hopefully be representative of something the structure does in the real world. Think about your loading case carefully.


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## jucasan (Mar 18, 2012)

Thank you guys for the response. The reason because I neglect the shock mount was for sinplification. Don't want to get too crazy yet with forces and loads. 
This is the window I get when I open SimulationXpress.

https://i850.photobucket.com/albums/ab61/jucasan/windows.jpg

But is totally different from what I saw in the tutorials online. You have the tree on the side and you have more options. There is a setting for this? I'm using SW 09. I'm trying to change the deformation scale and can't find the setting for that in this version.


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## felixv (Jun 11, 2010)

First of all, why don´t ask in a Solide Works or FEA based forum, much more knowledge there.
Before setting up your analysis take a pencil and draw a sketch take one minute to think about your loads.
As said the pivot point should be free to rotate, then you may think about the boundary conditions at the headset. Same about the load steps.

I don´t know about FEA in Solide Works, but are you able to define Elements and influence the meshing? Because these are the most important things in an FEA. If they don´t fit your result might be far away from reality and not only the value just everything.

The next thing is that you have sharp corners in your construction and these are stress riser and will keep your results far away from reality.

And FEM software is more like a calculator than an office programm. There is no learning by doing as long as the user don´t know what he is doing he never will get a valuable result. So here is the advice, get you a book learn about the theory behind then you will make progress much faster...


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