Planetary Ring Gear Stress & is Aluminum OK? 3

[TimtheToolMan]

How do I calculate the stress on ring gear? I know stress on planets and sun gear.

I want to find out if 7075-T6 will work for ring gear?

This is an extremely slow application and very low life is needed (a few hours at rated torque)

 

[paulliu]

My stress calculation experience was that
the stresses in the ring internal gear are lower than
those at the planet gears.

As you know, FEA can always be applied to calculate
the stresses if you don't have other tools.

 

[diamondjim]

Roughly the allowable stress for
aluminum vs steel is 65 percent
of that for steel. You might see
more wear from the aluminum gear
as it tends to eat or wear the
steel at a quicker rate than steel
on steel. The Y factor for an internal
gear is approx. .54 and for the
smaller external planets probably
around .36. This may be more than
you wanted to know.

 

[TimtheToolMan]

The two above posts will get me where I need to be and from different directions. I do a lot of FEA but have not used it for gears and comparing FEA results with real world results and hand calculations will work fine for my applications.

Thanks!

 

[Philrock]

AGMA standard 2001 can be used to calculate contact stresses. AGMA technical paper 97FTM7, Bending Load on Internal Gears of Planetary Gear Sets, by H. Linke and C. Jahn, can be used to calculate bending stresses. In addition to the kinds of bending stresses found in external gear teeth, there can be significant stresses in the ring, at the major diameter - especially if the ring is relatively thin. This techincal paper addresses both kinds of bending stresses.

Aluminum is not generally recognized as an acceptable gear material because it does not do well with sliding contact. However, since your life requirement is short, you may be o.k.

 

[TimtheToolMan]

Thanks for the sources and I will get the AGMA paper. A paper can be seen on:

http://rclsgi.eng.ohio-state.edu/~wu/REFERENCES/2001_kahraman_JMD.pdf