Shell Accuracy, small radii

[rubenvillarreal]

Following the e-Learning program.

First they say that shells are not very accurate at areas of small radii. Then they say that in comparison with shells, solid elements are not accurate at areas of small radii.

So, models with small radii, (as a bike for example), should be simulated using shells idealizations or solid elements?

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[rubenvillarreal]

For reference, a bike snapshot:

[TomD.inPDX]

there are several factors you are dealing with that will throw off your numbers.  Most importantly is the facet size and distribution.  That is what the analysis is done on.  Small rounds and fillets may just look like a chamfer.  Default analysis settings won't do these areas justice.

As for the cosmetic rounds pointed out in the image, they mean very little to the overall analysis.  I may even remove them for a simpler analysis.

So you know, I am not an analysis guy, but in almost every instance where I've reviewed or provided input for analysis, the model was always simplified geared to the study being performed.

[unickque · Accepted solution]

I would start with shells (if possible) and even take out the small radii at first. Then see what the stress in your model looks like. These radii probably don't cause any stress concentrations at all, due to the overall shape of your part. If one of these small radii does show a high stress you may be forced to use solid elements, because -as you showed in your first post- the thickness may be too thick to get good results with shells. In that case it may be possible to model only a detail of your part with solids, and apply known displacements or forces at the boundaries.

[rubenvillarreal]

Thanks Antonius and Patrick for your help!