FEA vs beam theory in bones - Max. Principal and Von Mises
FEA vs beam theory in bones - Max. Principal and Von Mises
(OP)
Hi, I'm running some FEA models of long bones in Abaqus.
I've extracted the cross-sectional properties at midshaft, and I've calculated what the predicted bending stress would be according to Euler beam theory applying the same bending load as FEA.
When I extract stress values at midshaft from my FEA models, I get values ~20% higher for von mises, and ~30% for max. principal than predicted by beam theory.
I understand that Euler Bernoulli ignores the effects of shear, which could be quite significant, as these bones have a fairly low l/d.
My question is: is it typical for Von Mises stress to be lower than Max. Principal stress?
And wouldn't we predict Max. Principal Stress to be closer to the values predicted by beam theory than Von Mises?
Appreciate the help
Cbrassey
I've extracted the cross-sectional properties at midshaft, and I've calculated what the predicted bending stress would be according to Euler beam theory applying the same bending load as FEA.
When I extract stress values at midshaft from my FEA models, I get values ~20% higher for von mises, and ~30% for max. principal than predicted by beam theory.
I understand that Euler Bernoulli ignores the effects of shear, which could be quite significant, as these bones have a fairly low l/d.
My question is: is it typical for Von Mises stress to be lower than Max. Principal stress?
And wouldn't we predict Max. Principal Stress to be closer to the values predicted by beam theory than Von Mises?
Appreciate the help
Cbrassey





RE: FEA vs beam theory in bones - Max. Principal and Von Mises
Tobalcane
"If you avoid failure, you also avoid success."
"Luck is where preparation meets opportunity"
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
your FE, presumably solid elements, includes a whole bunch of things that your My/I calc doesn't, shear delection being one. if you want to validate your modelling, i'd start with something simpler, like a beam element, which should be much closer to My/I.
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
"... but then i'd stay away from brittle materials in the 1st place."
The OP is talking about analysing bone - I guess god got it wrong when he made us with brittle bones - he should obviously have created us with nice ductile bones!
http://julianh72.blogspot.com
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
"On the human scale, the laws of Newtonian Physics are non-negotiable"
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
i guess i'm not god ...
RE: FEA vs beam theory in bones - Max. Principal and Von Mises
As far as god and intelligent design go...why'd he/she put the amusement park so darn close to the sewer outlet?