how to find crack initiation in gear tooth root
how to find crack initiation in gear tooth root
(OP)
Hi all,
I am doing gear tooth failure analysis for that i could know the following in fracture mechanics:
1. How to find crack initiation and crack propagation ?. (i found some articles about crack propagation but still i dunno about crack initiation, i mean to find a, where it initiates and what r the parameters associated to crack initiate)
I hope someone have a solution or ideas. thanks in advance.
regards,
lmgk
I am doing gear tooth failure analysis for that i could know the following in fracture mechanics:
1. How to find crack initiation and crack propagation ?. (i found some articles about crack propagation but still i dunno about crack initiation, i mean to find a, where it initiates and what r the parameters associated to crack initiate)
I hope someone have a solution or ideas. thanks in advance.
regards,
lmgk





RE: how to find crack initiation in gear tooth root
RE: how to find crack initiation in gear tooth root
RE: how to find crack initiation in gear tooth root
It is assumed that after \sigma n/N>1, cracks will be initiated somewhere on the gear surface. Mostly it would be at the root. Use the FEA to calculated stress intensity factor at the crack tip, there are relationships between this stress intensity factor and crack propagation speed dx/dN, then you set up the crack depth criteria. Lets say you set 1mm depth for the crack inspection criteria. A gear with crack depth more than 1mm will fail the inspection. From the dx/dN value you can get the life (cycles) from 0mm crack to 1mm crack.
The total gear life is the fatigue life + 0mm to 1mm crack life.
Most of the time, people will just replace the part after it reached the fatigue life limit, unless the cost to replace the part is so high.
As I said, I don’t think there is a crack initiation theory in crack analysis. Usually it is assumed the crack is initiated by a small imperfection on the surface. You have to assumed the worst case - crack at where the max stress intensity factor is. Or if you got some gear already failed, examine the crack location of your gear.
RE: how to find crack initiation in gear tooth root
RE: how to find crack initiation in gear tooth root
RE: how to find crack initiation in gear tooth root
Take a look through the publications at the following NASA website:
http://www.grc.nasa.gov/WWW/5900/5950/Publicat.htm
There are several that discuss gears, crack detection, finite element simulation, etc.
RE: how to find crack initiation in gear tooth root
RE: how to find crack initiation in gear tooth root
AGMA 1010 "Appearance of Gear Teeth - Terminology of Wear and Failure"
AGMA 912 "Mechanisms of Gear Tooth Failure"
CETIM Publication "Aspect des dentures d'engrenages apres functionnement"