FATIGUE CHARACTERIZATION
FATIGUE CHARACTERIZATION
(OP)
I´d like to know how to characterize a material to know their fatigue properties, I was looking for information and I didn´t find anything.
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RE: FATIGUE CHARACTERIZATION
Some steel tables does include a unmodified fatique limit stress, noted as Se. This can be used instead of half the tensile strength.
RE: FATIGUE CHARACTERIZATION
If you want to know about the basics of fatigue in welded joints you will find some useful information on my web site www.gowelding.com
RE: FATIGUE CHARACTERIZATION
Fatigue design, Eliahu zahavi
Machine design an integrated approach, Robert L. Norton
You should find something in these.
RE: FATIGUE CHARACTERIZATION
RE: FATIGUE CHARACTERIZATION
Analysis & Representation of Fatigue Data by Joseph Conway and Lars Sjodahl
and
MIL-HDBK-5, Chapter 9 (http://www.grantadesign.com/news/battelle.htm)
The Conway & Sjodahl book is out of print but definitely worth the price. MIL-5 is the material properties bible for stress analysts working on defense projects.
To create a statistically acceptable fatigue design curve, you perform the following steps (Excel functions in parentheses):
1) Linear regression of S-N data, with S as the "X" and N as the "Y" (m=Slope(Y,X) & b=Intercept(Y,X))
2) This gives you an equation that looks like Log(N)= b + m*log(S)
3) Compute the standard error of the estimate (STEXY(Y,X)
4) Your design curve is Log(N) = b + m*log(S) - k*see
5) k is a function of how "safe" you want to be. You can set k to 3, giving you a "-3sigma curve." It is better to use k as a function of the number of specimens you tested. There is more detail about that approach in the MIL-5 reference cited above.
Doug
RE: FATIGUE CHARACTERIZATION
Usually, X is log(N) and Y is log(S). You can try other transformations, but as I described the process, these should be used.
Doug