FEA for Gear with high stresses at rim
FEA for Gear with high stresses at rim
(OP)
Hi, i am analyzing a gear using FEA methods to assess the strength capability of various regions except for tooth bending which is analyzed using AGMA standards. My question: If the the FEA shows high stresses below the gear tooth does this area need to be assessed considering the rim thickness factor is taken into account within the AGMA standard for determining tooth bending stresses?
It seems to me that I dont need to assess this location below the tooth assuming AGMA shows tooth bending to be acceptable. A crack would never initiate below the tooth(i.e. at inner diameter of rim), it would initiate at the tooth base radius....let me know if I am wrong.
It seems to me that I dont need to assess this location below the tooth assuming AGMA shows tooth bending to be acceptable. A crack would never initiate below the tooth(i.e. at inner diameter of rim), it would initiate at the tooth base radius....let me know if I am wrong.





RE: FEA for Gear with high stresses at rim
This might help, look at page 22 it's shows the root of the tooth and yes there is a possibility that a crack could form there. I am not sure whether AGMA covers this or not.
http://www.dtic.mil/get-tr-doc/pdf?AD=ADA380656
RE: FEA for Gear with high stresses at rim
The AGMA standards directly refer to this as the 'backup ratio' but, as mentioned, does not cover the specific geometry of the part.
Some handy info here from Cornell Uni.
The work done is similar to that shown in the NASA document that desertfox provided.
http://www.cfg.cornell.edu/projects/spiral_bevel.h...
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
http://www.aussieweb.com.au/email.aspx?id=1194181
RE: FEA for Gear with high stresses at rim
Lastly, as desertfox and gearcutter noted, for safety critical gear applications it is important to ensure that your gears never experience a fracture between the tooth root fillet and the rim ID. This type of failure is usually catastrophic and results in complete loss of gearbox function. Instead, the rim should always have sufficient thickness to ensure that any fractures originating in the root fillets propagate through the tooth rather than through the rim. A gearbox can often continue to function with the loss of a single tooth from a gear. As a rule of thumb, gears designed for critical applications usually use a minimum rim thickness below the root equal to 1.0 times the tooth whole depth.
http://www.dtic.mil/dtic/tr/fulltext/u2/a398842.pd...
http://www.dtic.mil/dtic/tr/fulltext/u2/a312521.pd...
Hope that helps.
Terry
RE: FEA for Gear with high stresses at rim
http://www.dtic.mil/dtic/tr/fulltext/u2/a239500.pd...
RE: FEA for Gear with high stresses at rim