Limit on SCF
Limit on SCF
(OP)
Hi all
I have a kind of philosophical question. Is there an upper limit to a SCF (Stress Concentration Factor)? If you have a perfectly 90 deg corner without any radius (fillet), would the local stress in the corner be infinite?
I have not been able to calculate one with FE analysis. The finer I make the mesh in the corner, the higher, but also more local, the stress.
This is (usually) not a real life problem because: 1. It is not possible to manufacture (machine) a sharp 90 deg corner and 2. your material will be ductile and redistribute the high local peak.
But I think I have encountered such a case with composite material. The process is capable of producing a (almost) sharp corner and the composite material is brittle and will not redistribute the stresses. This design has been proposed due to easiness of manufacturing, (rotational winding of GF) and I have cautioned this design.
I would really welcome your opinion on this matter, before I tell the manufacturing people that they have to find another (and more expensive) method.
Thanks in advance.






RE: Limit on SCF
RE: Limit on SCF
RE: Limit on SCF
I will try to be more precise.
My question is: If you have a perfectly 90 deg corner, will your local (very local) stresses be infnite?
RE: Limit on SCF
In reality no, as the stress is redistributed.
RE: Limit on SCF
I find that to avoid convergence problems I always describe corners with a min of 15 degree angle between one face another, or to put it another way always have a min of 6 elements around any radius.
This link gives a reasonable explanation as to why a 90 degree bend makes a singularity. http://andreweib.wordpress.com/2010/12/14/stress-s...
RE: Limit on SCF
The background for rising this question is that a nearly perfect 90deg corner and almost no redistribution would be the case with composite materials. So I'm left with the Stress Concentration. I think we will have to find another manufaturing process, that does not leave us with a 90 deg corner.