FEA

[leyione]

I was wondering if any one coiuld help me with a manual or Tutorial on Design optimization of chain sprocket using FINITE ELEMENT ANALYSIS.pls send to my email address....Leyione@yahoo.com...thanks!

[Drew Price]

1) Does sprocket geometry meet packaging and desired gear ratio requirements?

If yes, --> 2).
If no, --> 1).



2) Does proposed loads at chain and sprocket mount interface meet expected loads sprocket will see during service? (consult mechanical element design handbooks, such as 'Machinery's', or ask a professor for guidance).

If yes, --> 3).
If no, --> professor (preferably a smart one, who has hot PhD candidates).


(PERFORM FINITE ELEMENT ANALYSIS NOW)


3) Does sprocket deform under proposed loads seen in 2.?

If yes, modify design, then --> 3).
If no, --> 4).



4) Does sprocket meet lifecycle requirements for cyclically loaded structural element based on materials used and expected shock loading? (consult fatigue loaded component lifecycle design tables, or professor from 2).)

If yes, --> machine shop.
If no, --> 3).



Congratulations, you can now perform FINITE ELEMENT METHOD driven design.



Go build a race car.



Best,
Drew

[Francis Gagné]

Might I add that FEA is an APPROXIMATIVE solution. Please don't believe all the colors it shows you!

I recommend that you read a bit about FEM theory before starting out to do analysis.

Remember, the FEA program outputs are only as good as the inputs you give it. Also it is limited by the hypothesis of the program and the one you make on applying the boundary conditions. You will probably not be able to estimate the stress on the tooth, or at least the surface stress. For this, there are already much good literature to make the right choice of gear sizing (Sorry, I don't have any to cite). For the structural part of the sprocket, since it is a pretty simple piece you should be ok for a first analysis. Stress near edges or blocked displacement might go very high which is not necessarily relevant to reality, the main reason for this is because you state that the bolt (for example) is infinitely rigid and that the hole is bonded to it which is obviously false.

Since your piece will probably have some bending components I suggests you use 8-nodes Hexahedral elements (Mid-side nodes in ANSYS) if your FEA program offers it.

Also, validate yourself with a reliable analytical model to see if you're analysis result are in the ballpark. FEA is a great tool for helping you get good design the first time, but it is not real life either.

For guideline of using the material efficiently you can inspire yourself from existing sprocket models (Google is your friend). A good design should have the mean stress as high as possible in comparison to the peak stress. Low stressed material is unnecessary material.

Good Luck!

[John_Burford]

Use Altair’s Optistruct topology optimization software. Optistruct guides the design to maximize stiffness and minimize mass. The software, like a DOE, finds the sensitivity of adjusting the mass and modulus of elasticity of each element in a FEA mesh. The optimization iterates to find the most needed load paths. In the case of a sprocket a topology optimization would show you the best pattern of cut outs.