Shell Elements: TRI6 vs. QUAD8

VMH

Just a comparison between quadratic shell elements, tri6 and quad 8. Attached are plots of them side by side with the "Max. element size" in the Mecway mesher.

[Deleted User]

I have sometimes gotten results where the plot is black, like yours. I don't know what that means though. I don't think that happens with solid elements. Curious if Victor can shed any light on that.

VMH

When we set our limits (maximum and minimum) on the contour plot, we may have black contours which mean they are outside of our defined limits. For the comparison above, I set my maximum limit at 21,600 psi so we are comparing against the same contours.

Also,say if allowable von Mises stress were not to exceed a certain value say 21,600 psi (0.6 x material yield of 36,000psi), then any contours that are black mean that they exceed my maximum value. Then I need to take a look into that area.

VMH

For shell elements where we have upper surface, bottom surface, and midplane, we have to set the max. limit (or min. limit) for all three at the same value to have them plot correctly.

[Deleted User]

hmm, interesting. i haven't messed with changing the legend. so maybe the software isn't setting the max high enough?

VMH

For all of the analysis I've done with simple and also complex geometry using shell or solid elements, I haven't seen any black contours unless I set a user-defined maximum and/or minimum.

[Deleted User]

i have seen the black areas appear when doing tests of shell models and using the von mises plot. i haven't changed the legend, don't even know how to do that. it would have never occurred to me to mess with the legend. i don't think i have seen the black areas with solids, but my memory of the issue may be incorrect. the next time i see something like that happen i will post it.

it's good to know it means the data is out of range. until now, i just thought it was some kind of error with shell models.