Structural simulation of pressurized tube - constraints?

Forum|Forum|3 years ago
February 16, 2023
3 replies
5314 views

Hi,

I would like to simulate in Creo 4 the mechanical stress and deformation of a thin-walled tube under an internal gas pressure.
I am having problems finding the best constraints for the results that I want.

Ideally, I would like to constrain the tube around its central axis. So that the resulting deformation of the tube wall is axi-symmetric around the tube central axis.

But I can't find a way to constrain the tube around its axis.

The only contraints that lead to some results (although not the ones I want) is to use the (flat) starting surface of the tube.

If I use the 'Planar' constraint (or Z = fixed, X and Y free) I get stresses that seem acceptable, but the deformation is wrong and not axi-symmetrical.

If I fix the surface in X,Y and Z, I get a result, but as expected, the deformation is 'weird'.
If I constrain as a 'Pin', that does not work.

Simulate

Best answer by EddyVE

I think I have found a way to achieve what I had in mind.

First, create a new coordinate system, but make sure it is a cylindrical one. Put the CS on the tube axis, with 2 datumplanes as references.

Define displacement for the end surface of the tube, where you use the cylindrical CS as reference. Fix Z and Theta. Keep R free.

This solves into a nice axi-symmetric deformation, and the VM stress matches my manual calculation.

To check the diameter deformation, I have to use X or Y deformation. Using 'Magnitude' takes the shortening of the tube into account, which I don't need.

tbraxton

22-Sapphire II

This article outlines the principles used to approach constraints of this type of problem. See the 3-2-1 method in particular. You should take advantage of the axisymmetric symmetry of the pipe as well when possible.

https://www.digitalengineering247.com/article/free-floating-fea-models/

E

EddyVE

Author

12-Amethyst

Thank you!

That is an interesting article, as it clearly pin-points the problem I am facing too: to create a decent 'fixed world' constraint so that the calculated results display what I want to see.
The 3-2-1 method is perfect to constrain the model if you are only interested in stresses. My problem is that I am also interested in deformation. And to show deformation, I want to use a reference point (the tubes axis) where there is no geometry (no material). So I can not place a node there.

I think I found a way. See my other post.

E