general question wrought bar vs forging 4

[mfgenggear]

Has anyone tested for stress values
wrought bar vs forgings, steels like AISI 4340, 9310
Gears in general

 

[stanweld]

What are you asking? Comparisons of forged & machined gears vs machined gears from bar stock?

 

[mfgenggear]

yes thats exactly it.
sorry for the confusion.

machined from bar vs machined from forgings.

 

[TVP]

There are two published papers/reports of which I am aware that document improved performance of forged + machined gears vs. machined-only gears. Use the following links for more information:

"Comparative bending fatigue strength of precision forged spur gears" by O. Eyercioglu, et al

http://pep.metapress.com/content/yw2452134722268r/

"A life study of ausforged, standard forged and standard machined AISI M-50 spur gears" by D. P. Townsend, et al

http://naca.larc.nasa.gov/search.js...tchall%7cmode+matchall&Ns=HarvestDate%7c1&N=0

Both of these papers describe gears that were either through hardened or induction hardened, not case carburized. There is no question that for through harden applications, forged + machined gears outperform machined-only gears. However, for case carburized gears, the problem is much more complex, due to the many interacting parameters, e.g., surface roughness, retained austenite, residual stresses, etc. Here is one published paper that documents no significant difference between forged + machined gears and machined-only gears that have been subsequently case carburized:

"Three point load application in single tooth bending fatigue test for evaluation of gear blank manufacturing methods" by E. Akata, et al

http://www.sciencedirect.com/scienc...serid=10&md5=8cd2c2a7fc5fbcea859a494534f3e0cf

 

[metengr]

Here is another paper to review and looks to be applicable to your question

http://cat.inist.fr/?aModele=afficheN&cpsidt=2817001

Résumé / Abstract
To determine the bending fatigue strength of precision forged spur gears and to compare the results with those obtained from conventional cut gears, single tooth bending fatigue tests were carried out on both through-hardened and induction-hardened gear teeth. The gears were produced from rolled bar cut blanks, disc forged blanks or precision forged teeth blanks. For this purpose, a special test fixture was designed and built for an Amsler high-frequency vibrophore fatigue testing machine. The results show that the endurance limit of precision forged gears is significantly higher than those obtained from cut gears. The bending fatigue strength of forged gears was some 12.5 per cent higher than the cut teeth in a through-hardened condition and 8.4 per cent higher for the induction-hardened teeth. The effect of surface roughness at the tooth root area on the bending fatigue strength of the forged gears is also shown.

 

[mfgenggear]

Thanks guys
Much appreciated for the quick response.
All of you received a star.