Modeling Carotid Artery Bifurcation using Swept Blend

[haleyking11]

Greetings! I am an undergraduate student looking to model the carotid artery bifurcation based on a glass model that has been created for physical experimental purposes. Attached is my current model in a picture.

I haven't used Creo extensively in over a year and am really having trouble figuring out the best method of constructing this bifurcation. Here is an image of a generic 3D bifurcation very similar to what I am trying to do: fig2:Concentration Polarization of High-Density Lipoprotein and Its Relation with Shear Stress in an In Vitro Model - Open-i

The dimensions need to be very accurate because I will be performing CFD analysis after modeling it. I did three separate swept blends with hollow circles as my 3 sections to join the three segments together, but they do not interface well with each other and are not hollow like the sketches I made of them. Here is the process I took:

-1 sketch of the trajectory (one line with two lines extending off of it)
-3 separate sketches of the 3 segment ends (although I will need more sections to further distinguish changing diameters, I just did this to try and get the method down)
-3 separate swept blends joining all 3 segments together

Problems I am having include the swept blend not being hollow, despite the fact that I made two concentric circles for the sketches of the sections to account for the thickness of the physical model. The 3 sections also do not interface well together and "cut" into each other, I want that entire "forking" area to be hollow just like the artery is in real life.

Please point me in the right direction of how to go about this, is swept blend the best way to model the bifurcation? And if so, how do I make it hollow and also not have the swept blends cutting into each other?

Thanks so much for any help you can provide!

 

[sjenk]

Not familiar with bifurcation in the slightest, so correct me if I'm wrong on any of my assumptions. It's essentially 3 tubes of varying cross section that intersect at a point, right?

I also am still learning creo and don't claim to know everything about anything, especially in the sweeps/blends department, but I'll still give some input to what I know. The cross sections of the sweep should have the same number of entities (edges, vertices, etc) in each, and depending on where you start sketching can make a difference and might be why you're having issues with the sweeps not being hollow, so fiddle around with that and see if that solves that problem.

As far as defining the tubes, you may want to try doing separate sweeps for the outer and inner diameters. The outer will create the solid outer walls, and the inner will be the volume through which the fluid flows, using creo you can create that volume and cut it from the solid outer sweep. This should give you more definite control over what happens on the inside of the intersection as well.

You also may be able to just do a shell on the "outer" sweep, but this assumes that the tube wall will have the same thickness everywhere and might make the intersection wonky.

Hope that helps somewhat

 

[mgnt8]

You should sweep surfaces instead, then merge them, then shell or thicken them

 

[moldman]

As far as the lack of "hollowness" - don't model that in the sweep, shell the resulting outside geometry. This won't help if the wall thickness needs to change. If that's the case, create the outside first, then create the inside geometry using surfaces, create plugs for the open ends and merge everything together.

 

[haleyking11]

You should sweep surfaces instead, then merge them, then shell or thicken them

As far as the lack of "hollowness" - don't model that in the sweep, shell the resulting outside geometry. This won't help if the wall thickness needs to change. If that's the case, create the outside first, then create the inside geometry using surfaces, create plugs for the open ends and merge everything together.

Thanks for the replies! So I should not use the swept blend, instead use the Sweep command? And how do I go about "merging" the sweeps? I tried to look up how to merge them and can't seem to find any documentation online or in Creo.

Thanks again!

 

[robert.c.allen]

Make it a solid first, then add rounds to all the corners in the bifurcation area, and finally shell the whole thing. Adding the rounds will ensure you don't get sharp corners on the insides of your shell.
If you have issues with shelling, then another approach: Since you are doing CFD, all you are really looking for is the inside geometry I assume, so you could also do the following:
1. Insert a big solid extrude at the top of your model tree that completely encloses your sketch.
2. Change all your swept blends from solids to cuts, and redimension them to match the inside geometry of your glass piece.
3. Now you can do your CFD.

 

[mgnt8]

I would build it all as surfaces. You can still use Swept Blend if you like, just select Surface instead of Solid. Then you need to "Merge" the surfaces. It's above the Editing tab with an icon that looks like an overlapping square and circle.

The reason I'd do it that way is that side radius connecting the CCA and the ECA. You might be able to fudge something in with a Round, but the real slick way to do is with a Variable Section Sweep and some trajpar equations.

 

[haleyking11]

I would build it all as surfaces. You can still use Swept Blend if you like, just select Surface instead of Solid. Then you need to "Merge" the surfaces. It's above the Editing tab with an icon that looks like an overlapping square and circle.

The reason I'd do it that way is that side radius connecting the CCA and the ECA. You might be able to fudge something in with a Round, but the real slick way to do is with a Variable Section Sweep and some trajpar equations.

Thanks so much! I am definitely making progress. Only issue I am running into is merging all three surfaces together. I can merge the CCA and ECA just fine, but it won't let me merge the third swept blend surface, the ICA. I tried doing them all in one merge, then tried doing two swept blends in one merge and merging that with the last one, but the part keeps failing to regenerate. Any advice on how to get all three swept blend sections merged together? I really appreciate the help!

 

[mgnt8]

Upload the part and we'll take a look

 

[srieger]

Doing it all as a solid and shelling it is much simpler than using surfaces. You will run into a lot less issues.