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Help with Geometry Preprocessing

Help with Geometry Preprocessing

Help with Geometry Preprocessing

Hi folks,
Kinda getting a hang of FEMAP but somehow finding it more frustrating than PATRAN (which is surprising). The demo videos posted by FEMAP is excellent and definitely help newbies with getting a foot in with the software.

Currently working on doing a local analysis of a cutout with fastener holes. It is important to get a clean good mapped mesh around the individual holes as well as around the cutout. I have attached a few pictures to illustrate my issues.

The geometry was imported as a Step files (would importing it in a native CAD format improve translation?). I am having issues with breaking down the surface before I mesh.

Image 2 illustrates the issue I had with offset. I was getting a discontinuous curves instead of a single one. Finally, I had to create a circle and trim it (tedious is what I felt).

Edit: I was able to join them using point to point option in geo edit (meshing tool box).

Image 3 illustrates the issue with curve splits and how I am unable to join them.

Image 4 illustrates the mesh I obtained after around 4 hours of work. There are still some trias in the critical zone which is undesirable for us (& the client). Hoping that experienced folks provide more insight in to perhaps easier ways of breaking down surfaces before meshing.

The images are clubbed together in a zip file. Sorry about that. Was not able to upload or attach more than one file to my post.

One more fact. I had to use mesh -> copy and/or reflect and/or rotate to obtain the mesh especially in the critical zone. I was unable to associate the mesh with curve/surface and hence when I meshed the surface outside of critical zone, it did not automatically retain the connectivity. I had to manually connect them and thus some trias sneaked in there. How can I ensure that association is maintained when I copy or reflect etc mesh.

Thanks in advance,
- B

RE: Help with Geometry Preprocessing


Could you post your step file?

Seif Eddine Naffoussi, Stress Engineer
33650 Martillac û France

RE: Help with Geometry Preprocessing

fig2 ... if you want a continuous arc ... then draw an arc (start,end,center) ... no?
fig3 ... FeMap breaks the circle into two lines. You can spend a lot of time to move the break where you show it, but I don't see why you need it ... FeMap distributes elements around the circle. one way would be to draw the PCD and break the fastener holes where they intersect the PCD, and make boundary surfaces for the 1/4 hole to the mid-pitch of adjacent fasteners ... if you can see what I mean.
fig4 ... look at the different number of elements in a 1/4 of an arc (associated with one fastener hole, yes?). the top (and bttm) hole has 4 elements, the next has 6, the next has 7 ... this'll mess up your mesh. three holes have 16 elements (which aligns with 4 elements per side (of the outer "square") but one (2nd up from bttm) has 15 ? the holes on the top (flat side) have 4 elements per side, but this reduces to three causing a transition.

For the body, outside of the four holes, make the quadrant from a single boundary surface (a five sided shape !) which you can mesh carefully to get a nice fan pattern. then mesh around the holes.

another day in paradise, or is paradise one day closer ?

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