Crack Propagation
Crack Propagation
(OP)
Hello all!
I'm working on crack propagation, and I have a few question about propagation.
From my understanding, fatigue will iniate a crack along the shear plane (so 45 degrees for tensile loading).
Then a crack will propagate perpendicular to the loading.
Then stress intensity factor is evaluated and the crack becomes unstable when K&c is reached.
But what I don't understand is that the loading is always assumed cyclic, ie fatigue for crack prop.
So the question is, what happens if the load is static rather than cyclic?
I guess paris'law is no longer valid, but is there a way of assessing propagation?
Is it related to the R-curve?
Thanks a lot for your help!!
Cheers
I'm working on crack propagation, and I have a few question about propagation.
From my understanding, fatigue will iniate a crack along the shear plane (so 45 degrees for tensile loading).
Then a crack will propagate perpendicular to the loading.
Then stress intensity factor is evaluated and the crack becomes unstable when K&c is reached.
But what I don't understand is that the loading is always assumed cyclic, ie fatigue for crack prop.
So the question is, what happens if the load is static rather than cyclic?
I guess paris'law is no longer valid, but is there a way of assessing propagation?
Is it related to the R-curve?
Thanks a lot for your help!!
Cheers






RE: Crack Propagation
RE: Crack Propagation
Well I was wondering if there is a pre existing crack, and the loading is not cyclic, is there a way to predict a potential crack propagation?
RE: Crack Propagation
in most cases it is fatigue crack growth that we're interested in ... an extension of traditional fatigue analysis. Fatigue analysis tells us that small cyclic tension stresses can cause failure. Traditional fatigue doesn't (expressly) consider the active crack growth phase (since it is so much shorter than the crack initiation phase). Damage tolerance says assume a crack exists, how quickly will it propagate?
another day in paradise, or is paradise one day closer ?
RE: Crack Propagation
I understand better the idea and the influence of fatigue.
So if I want to investigate on a potential crack propagation under constant loading, then I should have a look at residual strength of the material with the crack, is it right?
Cheers!
RE: Crack Propagation
but if you're looking at static load, that's technically a fracture problem, not a fatigue problem.
If I recall, fracture problems are governed by stress intensity inside the "singularity dominated zone" at the tip of a crack. There were a bunch of ways to solve for the stress intensity (K_I?).. I remember using Westergaard's solution a lot, and Irwin?
Hope that helps
RE: Crack Propagation
another day in paradise, or is paradise one day closer ?
RE: Crack Propagation