Spur Gear Stress Calculation 2

[Rnewcomb11]

Hey everybody,

So a quick overview, currently at my internship I'm helping the mechanical engineer with some stress analysis on gear teeth. I can't get into the details of the design because it is all proprietary and somewhat confidential information, but essentially it is a change gear (spur gear with an inner keyway) that is subjected to stress with a dog brake periodically. It's in a motor that has a solenoid brake system that engages the change gear with a dog to hold the gear in place and then is released to continue motion.

My question is, how can we accurately calculate/model the stresses the gear is subjected to? We've attempted the AGMA method and the lewis equations but we're finding discrepancies in our calculations. I think because the AGMA method factors in fatigue stresses and is intended for gears that are constantly meshing. This application is more like shock loading when the brake is engaged. We have calculated the transmitted force and picked a gear with the specifications we want, we just need an adequate formula to quantify the stresses for our design. Any help would be greatly appreciated.

 

[gearcutter]

how can we accurately calculate/model the stresses the gear is subjected to?

If, as you say, this needs to be done "accurately" then I would highly recommend that you engage the services of a gear design consultant.

Without a drawing and some numbers; nobody here is going to be able to give you much help.
It sounds like it's a static load so the Lewis equations will show you how to treat a single tooth as if it were a beam.





Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[tbuelna]

AGMA 908-B89 and AGMA 2001-D04 describe a very detailed approach for precisely calculating tooth bending and contact stress of involute spur gear meshes. You'll probably need to do some iterating to determine what relative position of mating teeth at the mesh produces the worst case for the brake impulse loads, and then use that geometry for a static analysis. It won't be easy, but the AGMA documents provide all the equations you need.

It will be a great learning experience and you should be able to complete the task before you go back to school in the fall.

Best of luck to you.
Terry

 

[Rnewcomb11]

Thank you for the replies. I suppose when I said "accurately" i meant a calculation that could give us an indication to see if the stress is within the yield range of the material. Just a basic formula really. I feel like I'm guessing with AGMA approach. The variables like "mounting factor" and "dynamic factor" are tabulated, but there are ranges in the tables I'm accessing. Depending on what numbers I select for my factors in the equation drastically affect the bending stress the tooth is experiencing. I'll take a look at the AGMA 908-B89 and AGMA 2001-D04.

 

[DesignerGuy16]

Google NASA Reference Publication 1152

The answers you seek are likely within, and more.

James Spisich
Design Engineer, CSWP