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Modelling of bicycle suspension

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aclugston519

Mechanical
Feb 25, 2015
3
Hey,
so as part of my third year university project we have to design and build a folding bicycle, as part of this process we have to show some form of FEA analysis. I have done one module in abaqus that really didn't prepare me for what I needed to model a complete 3D FEA analysis and as such I have taught myself through what was available online and trial and error. I have now got a running model in place that gives results, however I feel that the deflection represented by the model is considerably larger than what it really ought to be.
Here is the frame before deformation is plotted: Link
And the frame after deformation is plotted: Link
The frame has been imported from solidworks in several parts and all interactions between parts should be correct. The spring itself is modelled as a 75mm 550 lbs/in spring mounted between two aluminium blocks to simulated a normal bicycle suspension spring.
Any help in this would be greatly appreciated and I apologize if this is not the correct way of showing screenshots on this forum, it's my first time posting.
Kind regards,
Adam

 
 http://files.engineering.com/getfile.aspx?folder=68e6b631-349e-449f-afd9-87b44a2654f5&file=Before.png
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Having just received my confirmation email I realize that my post is in violation of the students rule, however I am not some "lazy students posting homework", I have put about 60 hours into this and have hit a bit of a road block with what to do next in regards to more accurately modelling the spring and any help would be kindly received.
Kind regards,
Adam
 
Without more information here are a couple of guesses.

Do you have consistent units? Your spring definition was stated as "75mm 550 lbs/in"

When viewing results Abaqus can scale the deformation. Make sure it's set to 1 if you want to see the actual deformation.

I hope this helps.

Rob Stupplebeen
 
looks like the viewer scaling is set to a number larger than 1, mentioned above.
 
As the others have mentioned, the deflection shown is exaggerated for easier viewing. If you look at your legend, your maximum deflection magnitude is less than 2 mm, which seems reasonable.
 
Unit are all correct, i quoted them as that more because I had built the model in mm in solidworks, converted to meters in abaqus and the spring I'm trying to model is 550lb/in but I converted to N/m before entering, so many different units it's becoming difficult to keep on top of them all.
As for the viewer scaling, I wasn't aware if that was something that could be altered, as I mentioned I have been teaching myself through mostly trial and error so a lot of what is probably basic and silly things are over my head still. How would I go about changing the viewer scaling? I've looked through all the settings and can't seem to spot in anywhere.
Thanks for the quick responses.
 
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