SAE Keyhole Benchmark

[lLouie]

Hi,

I would like to validate the fatigue analysis program I am using with the attached example. The results for crack-free specimens are quite consistent and reliable.


However, for analyses involving a 2.5 mm crack, despite reading many articles, I am unsure about the approach I should follow.
How should I model the crack? Should I model it at all?


For the CR1 specimen, while the total life is calculated as 690,500, how can I obtain a result closer to 605,000 for the 2.5 mm crack case?

https://www.efatigue.com/benchmarks/SAE_keyhole/SAE_keyhole.html

 

[rb1957]

IMHO I would not do "fatigue" analysis for a crack. Yes, I know people (generally in some sales or management position who don't know better) do, but fatigue is a polished (uncracked) specimen and cracked specimens do "crack growth" (or damage tolerance) analysis. The point is that fatigue analysis is all about crack initiation and compared to this duration the period of crack growth is small enough to neglect ... most fatigue tests the specimen is entire intact or broken (binary). Damage tolerance analysis assumes a crack and is all about crack growth, particularly detectable (using whatever inspection you want) crack growth.

Yes, to get a crack life you need to model the crack. You're working to an example, so how does that method differ from yours ? The difference will be very small, quite possibly a bunch of round-off errors. I assume you've followed some SAE procedure, so try varying the parameters very slightly, one at a time then in combination.