Static spur gear calculation acc. DIN 3990

[arnoldh]

Dear all,

I have to make a static spur gear calculation acc. to DIN 3990. In part 5 of this standard, diagrmms are available, which show the fatigue limit for pitting. Since I will have to calculate a static case, I am not sure if these values are appropriate for my calculation. E.g. for 42CrMo4 @ 50 HRC, the fatigue limit is appr. 1150 MPa, the static limit would be appr. 1600 MPa.

In general, I would expect I could use the higher values for a static calculation. Can anybody tell me if I am correct?

Many thanks in advance and a merry christmas to everybody!

Regards,

Arnold

 

[dimjim]

You are correct depending on your application and
speed or rpm of the gear set.

 

[DaPE]

Yes, you are correct. Allowable static limits are always higher than allowable dynamic limits that eventully lead to some type of gear tooth failure, e.g., pitting. I believe Miner's rule can be applied to ascertain practical operational stress limits.