stress concentration factor - fine mesh FEA 1

[magicme]

hello

i can't get any universal agreement on this question, and it seems it should be simple.

i have a finite element model (ANSYS) of a hollow stepped shaft with a fillet at the root of the step. i model a fine mesh (at least 10 elements from OD to ID ) and looking at bending and torsion in the shaft. the mesh is very fine when compared to the radius of the fillet (3").

i argue that the stresses output by the model are valid as-is, while some of my partners say i need to add stress concentration factors on top of the ANSYS stresses. i think they are wrong --- if the mesh is fine, the stresses will implicitly include "stress concentrations".

i have searched the previously asked questions and can't put together a direct answer to this question.

any comments would be appreciated.

regards

magicme

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"not all that glitters is gold"

 

[gurmeet2003]

Corus,

I was thinking use a coarse nearly uniform mesh. There will
be some areas that will stand out because of high stress (relative value, red color). These may be areas that already have a fillet. If a location is a sharp corner and has not been modelled with a fillet I guessed at a stress concentration value of 3 (a preliminary value).

I know a coarse mesh and a sharp corner will not give accurate results. But we are only trying to get some preliminary values.

What do you think? If you do not agree with above what course would you follow to check which sharp corners are important and need to be modelled more carefully?

Gurmeet

 

[EdR]

GURMEET2003:

Why would you assume a SCF of 3 for a sharp corner??? That is the SCF for a hole.....If I remember correctly the SCF for a sharp interior corner is infinite theoretically.....don't remember what is is for an exterior corner but stress should be minimal for exterior corners having no load...check a reference book!!!

Ed.R.