How do I intelligently cap complex splined surfaces?

Member

Hello!

I have the following crescent shaped geometry, in stress analysis the sharp edges seem to give me stress singularities and accordingly I wish to smooth out the edges or add a round cap to both sides of the prismatic structure.

Here's what I tried till now:

-1) adding an ellipse and a point in front of the surfaces and blending such that the surface smoothly converges into a point. This works only when my surface is more elliptical and completely fails (produces unmeshable self intersecting surfaces) when the surface shape is more crescent like.

-2) creating an offset curve and moving it abit forward to blend into, this creates a sort of round as seen in the setup below. The main problem is that the polynomial surface creation here is extremely unstable, either it doesn't give me a preview, or if it created a polynomial blend then it very often doesn't combine with the other prismatic part, or if it does combine the surface becomes corrupted! Using linear blends is much more stable but it creates a chamfer like situation and not a round and I'm not sure if that will fix it.

I have an added constraint that I can't extend the structure too far from the original prismatic face

If anyone can help or advise on how to add a nice smooth round to the caps I would be extremely grateful! I've been banging my head all week on this problem. I added the file in the zip in case anyone wants to take a look themselves

Thanks!

• Forum Coordinator

if I understand your issue correctly then following options you can try.

1. Use pull command and give round or chamfer to edges of that face.
2. Split single curved surface into say 6 to 9 surfaces. Then use the commands you are using to create surfaces at the end.

Regards,

Keyur

Guidelines for Posting on Ansys Learning Forum

How to access ANSYS help links

• Member

Hello Kyur,

1) I forgot to mention this but the round functionality with the pull tool does not work with these edges, it seems to be unable to work with splined edges!

2) I'm not sure what you mean when you say use the commands to create surfaces at the end

3) The attached file is the scdoc file, so don't worry about that!

• Forum Coordinator

In your images you have big surfaces. Please split them into say 6-7 surfaces. Then proceed.

Regards,

Keyur

Guidelines for Posting on Ansys Learning Forum

How to access ANSYS help links

• Member

Hello Keyur,

No need to open the attachments! I have uploaded all the images in the original post

I'm confused as to what you suggest I do after splitting the big surface into 6 surfaces, do I split the cap face or the curved surface?

Thank you!

• Forum Coordinator

Split both surfaces - cap and curved surface.

Once you split these faces then use blend tool to create surfaces.

You may also want to change shape of elliptical face.

Regards,

Keyur

Guidelines for Posting on Ansys Learning Forum

How to access ANSYS help links

• Member

Where did this shape come from? It looks like it was cleanly sliced from a much larger solid. It looks like the the much larger solid was from a CT scan of some bone.

To have accurate local stress results, the cut boundary must be far enough away from the area of highest stress in order to have no influence. You don't have that and rounding the edges is the wrong approach to fixing this problem.

I recommend you go back to the much larger solid and use that to get away from the problem of high stresses at the cut boundaries.