"...in a fatigue analysis, only Ktn can be used..." - Peterson

[olyoly]

Does anybody understand the subject statement from Peterson?

Here's the complete sentence from “Stress Concentration Factors” 2nd edition:

“In addition, in a fatigue analysis, only Ktn can be used to calculate the stress gradient correctly.”

The implication is that for a fatigue analysis, Ktg can not be used to calculate stress gradient correctly. This does not make sense to me since for the couple of examples that I worked out, the final stress value is the same whether I get it from Ktn x stress on net cross section or Ktg x stress on gross cross section.

What am I missing?

 

[rb1957]

i agree with your peak stress calc (either Ktn*net area or Ktg*gross area).

 

[olyoly]

Thanks for the post rb1957!

So you agree that, by extension, Peterson's statement doesn't make sense?

 

[rb1957]

i'd have to read it in context ... you have a pg number ?

 

[olyoly]

In my paper copy, it is Page 8 at the top. This is about the middle of section "1.2.1 Selection of Nominal Stresses".