post processing of results 1

[meher634]

Hello,
I would like to know how we report the stress results at a critical region ?( should be averaged at nodes or without averaged at nodes)
Thanks

 

[nagi]

I would use the averaged stress since it is usually closer to the exact stress value. The difference between the non-averaged values at a node is a measure of the error. If it is too large I would use a finer mesh.

Nagi

 

[Drej]

Ask yourself the question: what is the difference between averaged/non-averaged stress values? For a "critical" stress region, you will need to report the most accurate stresses, which in the majority of cases will be reported at the gauss point(s) of the element(s). Non-averaged values are taken directly from extrapolations to the nodes, while averaged values average the extrapolations at nodes.

-- drej --

 

[dollarbulldog]

Hi,

I normally don't look the stress results as nodal value. Most standard FE softwares provide average and non-average version of element result. Most of them are computed directly from Gauss points. As nagi said, the differece between average and non average results exhibits how accuracy the solution is. For theoretical converged solution, there should have no difference at all, since most elements are in constant state of stress.

Another hint is that if there is a high variation within a single element like some stress component change its sign (usually shear stress in beding dominated problem or normal stress in an incompressibility condition), make a refinement at that region or used enhanced strain element.
The result from that kind of mesh is usually lock in some way. This might be 200% or more different from the exact solution


Bests,

 

[nodepicker]

I usually use the element stress for the reasons as stated earlier in this thread. One has to be careful with the use of averaged nodal stresses. If there are varying thicknesses of shells connected to an averaged node, then it is not appropriate to talk about an averaged stress in the node. The same problem might occur if there is a curved surface.

Regards
Node picker