Corner Radii vs Notch Factor
Corner Radii vs Notch Factor
(OP)
We have been working on a part that is shaped like a horse shoe with machined bosses on the ends. Where the bosses connect to the horse shoe we have a generous 3/16 radius. When we run the fea we are getting very high stress concentrations on the corner radii. When we modify the model and reduce them the stress levels drop significantly. Obviously there is a trade off between too small a radius and too large. Although I would not have expected too large to make that much difference. I would have thought a 3/16 radius would be better for fatigue and notch factor than a 1/16 radius but it sure doesn't look that way on the results. Any thoughts?





RE: Corner Radii vs Notch Factor
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Corner Radii vs Notch Factor
corus
RE: Corner Radii vs Notch Factor
Just one comment on the second sentence by corus. I thought a coarser mesh overestimates stiffness, since it has fewer dofs (assuming typical shell or solid elements).
RE: Corner Radii vs Notch Factor
Thanks
RE: Corner Radii vs Notch Factor
There have been some investigations as to determining the stress level when considering a mixed-boundary condition. A group of Italians examined this problem and published their work : "Mathematical Theory of Elastic Equilibrium", by G. Grioli, 1962, Academic Press. Finite stress levels have been predicted when the non-symmetry of the stress tensor is assumed. Also, one should examine: "An Application of the Lagrangian Multiplier method to a Mixed Boundary Value Problem", by R. L. Citerley, J. Franklin Institute, Vol. 281, No. 4, April 1966 and the documentation associated with MSC Nastran's crack element.