Fatigue allowable at hole in steel plate

[trainguy]

Hi all.

Can anyone suggest what fatigue allowables I should use at the steel just around a bolt hole, where the bolt is loaded in tension/compression, as well as the reference used?

Looking for infinite life,
Bolt load fluctuates from -1460 to +1460 lb

Method of analysis - linear static FE
Load applied on a circle (not on a cylindrical surface)

thanks in advance,

tg

 

[GBor]

Check out

http://www.fatiguewizard.com.

Besides being a useful program addition to your FE, there is some good information.

 

[GBor]

Just found out his documentation link is broken. You may also want to look at

http://www.fatiguecalculator.com.

Not sure it will handle your specific situation, but, again, there is a lot of really good information.

 

[rb1957]

what does "Load applied on a circle" mean ? is the load transferred by a set of pins on a PCD ?

I'd suggest the method in Michael Niu's book "Airframe Structural Design", pp232, where he combines the bypassing stress and the load transfer to determine a stress concentration factor.

 

[EdR]

rb1957:

The stress concentration factor for a hole is 3.0

Ed.R.

 

[corus]

A general rule for infinite life is to take half the UTS of the material. If you're modelling the bolt load then bear in mind that the bolt, and steel, is prestressed so that the bolt doesn't see the full range of load. Presumably that also applies to the material around the hole.

corus

 

[hondaknight1]

You really need to find an SN curve for the steel which has been tested with R= -1, as your load is fully reversed. Although analysis on the stress on the hole may prove to find a different R ratio than that of the bolt. Then on this curve find the knee where the lifetime is about 10million cycles, the stress at this point gives you your endurance limit.
The 50% recomendation is only for polished steels with no surface discontinuities and with lower UTS, it is really only a special case. The endurance limit will lie anywhere below this and really depends on the steel grade and thermomechanical history. If you can find an S-N curve for your steel you will learn an awful lot.

 

[rb1957]

EdR ... you're correct for a hole in a tension stress, but the Kt for a hole with a fastener transferring load is significantly higher.