Mesh Quality Check

Hi,

Maybe topic does not refers to calculix directly, but I want to ask about mesh quality. How can I check mesh quality in gmsh or any other open source software? I want to plot aspect ratio, jacobian, warpage, angles, etc of my mesh elements.

In Gmsh this is quite limited, there are only 3 criteria that can be checked (using Tools → Statistics → Mesh):

  • SICN: signed inverse condition number
  • Gamma: inscribed radius / circumscribed radius
  • SIGE: signed inverse error on the gradient of FE solution

Salome Meca, on the other hand, provides a set of tools for mesh quality checks (available under Controls), including this window:

and contour plots of these variables. But it seems that it all pretty much comes down to aspect ratio anyway. At least when it comes to the standard 3D mesh quality criteria known in FEA.

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I saw this 3 criteria available in gmsh, but I don’t know how to interpret it.


Value in “()” is range of acceptable values? If yes, my mesh is good.
How about 2D plot, how to interpret it?



This is a count of mesh elements with quality parameter value?

The ranges in the brackets are minimum and maximum values of each criterion in your mesh. You will see this if you create a 3D plot of these variables, the min/max values will be seen on the legend.

When it comes to the 2D plots, they show the number of elements vs. the quality measure.

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Who know how this plugin works?


I have no idea and description from manual is not clear for me

[…]

Set 1 in the fields that you want to activate. For example, if you want to create a contour plot of the jacobian determinant, set 1 in the first field and in the one named CreateView.

Hi,

I am currently using gmsh to check element quality, I understand what does gamma stand for, but my question is about this specific value that is displayed in the statistics window (in this example it is 0.7997) how it is calculated and what does it mean? because I exported the xy data and tried with some operations like average and median but it didn’t match.
Could you help me in this, please!

Thanks in advance,
Cheers,
Farah

My method is really low tech but based on experience. Try to keep elements with a length to width ratio of about 1:1. For quadrilaterals, try to keep the corner angles near 90 degrees. Transition to smaller elements at inside or re-entrant corners or at holes where there could be stress concentrations.

I am not really too concerned about trying to measure the mesh quality on the first model. I remind the mesh and repeat the analysis to check for changes. If changes to the mesh seem to give similar results then I have confidence that the model is pretty good. If two similar meshes produce wildly different results, then I have no confidence in either mesh and try a third.

Hi Mati, I have made myself the same question, but didn´t find any solution by the moment. There is a specific tool made this, called Mesquite from Sandia Labs, that not only check the quality, but also modify the mesh to improve it, but again, dind´t find available an executable for Windows, maybe some compiler hero could bring us such tool :slight_smile:

After years of working with meshes, as @WilliamK says, one develop a good “eye” to catch badly shaped elements, too agressive changes in sizes, or poorly geometry representation (few elements in small features), or learn that if that bad elements are in areas with very low stress one can safely ignore it, or if the solver refuse to solve because of that… just delete it, one bad or missing element in a non stressed area will not change your results.

But… there are customers that ask for a mesh quality report, some often has a set of limit values for the parameters that you mention, so having this tool would be very usefull.

LS-Prepost probably has a tool for mesh quality, but somebody knows if is really free to use? And can be the meshes imported or exported to standard formats as inp or unv? I will take a look tonight if its usefull, but the last time that I tryed was a pain to use it, guess that worst than Salome.

https://www.lstc.com/products/ls-dyna

“LS-Pre­Post, which is freely dis­trib­uted and runs with­out a li­cense.”… but would be free for comercial purposes??? I just read in another site that is “free to use for any LS_DYNA user…”.

Best Regards

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I found in Salome more mesh quality controls, under Menu/Controls there are controls for 2d faces/elements and 3d elements. You can view a color plot with the desired criteria, or create also an distribution plot and even export the data to a txt file. See the pictures attached, for creating the distribution plot and export, the options are in the contextual menu of the graphical area.

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Hello,

i would recommend to take a look at Cubit from Coreform. This is a professional meshing software for creating high quality meshes. Cubit got all the quality checking tools you are searching for.

With their Cubit-Learn license you get the full functionality for free. The only limit is that you can’t export more than 50k elements.

Best Regards

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Even if you don’t want/need it, watch the vid’ it’s a classic

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ahh i forgot about that video. it’s hilarious.

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