"Deep" (non-surface) selection of elements

Rusticus

New Mecway user here.

Is there any facility for picking an element that isn't the one nearest to the user? What I'm getting at is, if I automesh an imported STEP file, there may be a defective element several layers deep within the mesh, flagged out with the big red "X" (it's happened several times).

How can I select that "deep" defective element instead of the element(s) on the surface? Am I compelled to fiddle around with clipping planes to try to get the right setting to remove the nearer elements from display, so that the "deep" element is now (effectively) the nearest?

Would it be possible to have some sort of "list select" function which could enumerate all of the elements which lie along the semi-infinite ray (give or take some tolerance - in pixels or whatever) defined by the cursor location? Many CAD systems (I've used a bunch) have this facility, which makes life somewhat easier.

If this function already exists, how can I access it?

Thanks for any pointers anyone can give.

Rusticus

Sergio

Could it be that if you run a simple analysis the solver tells you what element are wrong? Then you can select by element number. I don't remember having bad elements inside the geometry, they always appear outside near small surfaces or features.

Rusticus

Sergio -

That may be the way to do it. I'll try that out.

When I meshed the STEP, I had more than a dozen bad elements. I could see them on the screen, but couldn't figure out how to select them, except for a couple which were on the surface. They all seemed to be somewhat banana-shaped quadratic tets, even though I'd checked the hex dominant option. I tried regenerating the mash with selecting the option to keep mid nodes on the surface (something like that), but it was even worse as far as the number of degenerate elements. I'd thought if I could select the bad elements, I could break them up into multiple smaller elements.

I've reverted to sketching up the profiles, and revolving them, just to get something that can solve.

I had a couple of FEA classes 20 years ago in university, but I haven't much used FEA in anger in the years since. Feeling a bit rusty...

Thanks again for your help.

Rusticus

Sergio

One trick to improve the mesh is first mesh with lineal element, and then change the shape (order) of the element, so then it will add a node in the middle but not deforming the element shape to this bananas. Now I don¡t remember if Mecway have the option to mesh with second order elements, but not forcing the middle node to lay on the surface to create this similar mesh.

Regards

Victor

Making linear tets and converting to quadratic with straight edges is the same as what the automesher does when Fit midside nodes to geometry is turned off. It's off by default because it tends to make bad elements with the default element size settings.

Other solutions are reduce the max. element size, increase Min. number of elements per curve (if it's happening because of a tight curve like Sergio said) or add refinement at the problem locations.

Rusticus

Sergio -

Yes, Mecway's mesher can create quadratic elements from the outset. That's how I accidentally made the bananas.

It is possible that the STEP file has too large of sectional changes, or is otherwise difficult to mesh.

Victor -

Thanks for expounding on the behind-the-scenes of the automesher. When I get back to meshing the STEP solids, I will experiment with the max element size and min # of elements per curve.

For now, I am using drastically simplified geometry while I suss out how to tell Mecway what I want/need.

Rusticus