Von Mises Stress and Endurance Limit
Von Mises Stress and Endurance Limit
(OP)
Back when I was in school no one talked about Von Mises. I'd like to learn more about it. Whereas for simple bending or axial loading you can start out with the Endurance limit = .5 * Ultimate stress, is there a way to use Von Mises stress to predict endurance limit? Say, Endurance limit = .5 * Ultimate stress * ?.
I'm not looking for in-depth, "aircraft design" type design precedures. Just wondering if there was a good starting point for a "not super accurate" prediction of fatigue life.
I'm not looking for in-depth, "aircraft design" type design precedures. Just wondering if there was a good starting point for a "not super accurate" prediction of fatigue life.





RE: Von Mises Stress and Endurance Limit
In short, it's not a simple answer, but in general using principal stresses is the most conservative (i.e. safest) method. If you're not trying to design things on the razor's edge (as the do in aircraft where grams count) then Von Mises or Tresca don't really need to be applied.
There's a couple of good threads on this topic already, here's one:
http://www.eng-tips.com/viewthread.cfm?qid=123897
RE: Von Mises Stress and Endurance Limit
Once you have initiated a crack, however, you enter the realm of fracture mechanics. The crack will grow normal to the orientation of the maximum principal stress, and can change (abruptly, occasionally) as the crack grows if the orientation of the maximum principal stress changes. This has no relation to any invariant (von Mises, Tresca, etc).
RE: Von Mises Stress and Endurance Limit