contained volume tubular frame

[dakeb]

Hi,

I have created a tubular welded frame from square hollow
sections to go subsea, and I need to calculate the
contained volume of water to estimate it's mass for
lifting.

I'm a bit rusty on this, is there a way of easily doing
this by modelling, e.g. using cut-out? How would I do
this?

Bear in mind I don't want to end up with the volume
between tubes, just the volume inside the tubes.

Thanks

Dave
Edited by: dakeb

 

[dakeb]

As I am using the same tubing throughout the assembly I
did it this way: -

I suppressed all parts from the 3d cad model except the
square hollosec in the framework.

I analysed the total weight of the hollosec in Proe, it
came out to 5865kg

I modelled a 1m length of hollosec and analysed the
weight in ProE. It came to 63.95kg (i.e. 63.95 kg/m)

5865 / 63.95 = 91.71m total length of tubing

I modelled the internal volume of a piece of hollosec and
analysed the area of it in ProE. It came to 0.0138691 sq
m in cross section.

91.71 x 0.0138691 = 1.2719 cu m of trapped volume.

I still want to know how to do this by modelling and cut-
out though, in case I need to do it for an assembly with
variable sections.

 

[cpoirier]

Just an idea,
Put the frame in an assembly with a part called volume.
Use component operation and merge the frame to make one part out of the pieces.
Use a seed and boundary selection to get the all the internal surfaces.
Copy them into the volume part.
Solidify the surface set and use an analysis feature to get the volume. Make a cutting plane and use solidify again to represent different levels of fill if regulating buoyant force with air pressure. May even be able to use attitude in the assembly with a c-sys to investigate how stable the shape is. You can use the density and volume of the frame and the volume of the air space to get the buoyant force using parameters and relations in the assembly.

Sounds like you need an analysis feature, never used them, but know of them.

No doubt there are better faster ways, need to play with it.
Sounds fun. Care to share the file?

With some effort it may be possible to to it all in one part and come copy geometry features. You'll need to close up your weld gaps.

Good luck,
Chris

 

[kenppy]

There is a quicker way to do it, assemble your frame into a block encompassing the whole thing and component operations cutout, a bit of maths and job done. Don't know why I hadn't thought of it before when I struggled to close volumes.

 

[cpoirier]

Buoyant force is going to be weight of water displaced minus the weight of the structure.
So if the frame is used like ballast the internal waterline and volume is something you need account for. Wouldn't that approach just give you the volume/weight of the frame.

 

[dakeb]

There is a quicker way to do it, assemble your frame into a block encompassing the whole thing and component operations cutout, a bit of maths and job done. Don't know why I hadn't thought of it before when I struggled to close volumes.

Surely that also fills the empty spaces between the tubes which have to be deleted out?

 

[dakeb]

Just an idea,
Put the frame in an assembly with a part called volume.
Use component operation and merge the frame to make one part out of the pieces.
Use a seed and boundary selection to get the all the internal surfaces.
Copy them into the volume part.
Solidify the surface set and use an analysis feature to get the volume. Make a cutting plane and use solidify again to represent different levels of fill if regulating buoyant force with air pressure. May even be able to use attitude in the assembly with a c-sys to investigate how stable the shape is. You can use the density and volume of the frame and the volume of the air space to get the buoyant force using parameters and relations in the assembly.

Sounds like you need an analysis feature, never used them, but know of them.

No doubt there are better faster ways, need to play with it.
Sounds fun. Care to share the file?

With some effort it may be possible to to it all in one part and come copy geometry features. You'll need to close up your weld gaps.

Good luck,
Chris

Selecting all the boundary surfaces is going to be prohibitive, there are lots of tubes.

 

[cpoirier]

You may need to suppress any holes to do this.
Once you merge all the parts into one and they share all the same internal volume, select one internal surface (seed), Hold shift select another internal surface (boundary), on releasing you should highlight all the surfs except the boundary. Then once they are all selected Hold the CTRL key and add the boundary surf to the set. hit copy paste. bang you just got all the internal surfaces that enclose the internal volume. As long as the two surfs you used to make this set do not change and there are no holes the set should update with changes. The copy feature preserves the selection set for you while you work.

Chris

 

[dgs]

You can also use an external surface as the boundary and you'll get all the internals in one step, no need to add anything manually.

 

[cpoirier]

If you were to use a csys to position the part in an assembly and have a cutting plane for the internal volume you could find the writing moment with respect to the fill level and attitude of the structure. (need analysis features and some relations) I have seen this method in action at a web site where the Pro E gods reside. Leo G are you out there.

Your project sounds like fun.
Can you share any models to play with?

Chris

 

[cpoirier]

I meant righting moment, I have a very strange learning disability

 

[cpoirier]

Doug,
Nice trick. that works great!
Thanks.

 

[design-engine]

I use top down design to create a model of what would be hollow or water then do mass properties there.