linearized stress in pro mechanical

[napoleonm]

Hello every body.
REF: linearized stress.
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I am using Pro/e wildfire 2.0 with mechanical M130

I would like some suggestion about the following topic:

I need to model a pressure vessel under internal pressure, but due to the complexity of the model I can not use a shell model with the benefits of having the membrane and bending stress directly, as many pressure vessel codes request for a stress by analysis design (or simple to know the average stress values across a ligaments in a solid mesh model).

So, I need to go with a solid mesh; my point is to extract the membrane and bending stress from a solid wall thickness in the more stressed place.

Running under integrated mode, I would like to extract this values using the linearized stress query available in pro-mechanical.

The problem comes when trying to define the model, the massive

 

[napoleonm]

Problem solved using Volumen regions.


Msc. Napoleon Motaban.

 

[TrailBarge]

I used to work for a pressure equipment company and we did this stuff
for Section VIII, Div 3 vessels all the time.... in Mechanica.



Now, that being years ago, how did we pull this off? I seem to recall:



1: make a cut in your pro model to leave 1/4 remaining.

2: I forget if you do it in pro or mechanica (i believe mechanica), but
you draw a datum curve along the line of interest. Ususally, this
is someplace like the bottom radius or at the root of the first
thread. You want to be as perpendicular to the isostress lines as
possible, so sometimes a preliminary analysis is best. (I
remember that the curve at the bottom radius angled towards the head at
about 60 deg from the axis)



Make sure that the curve is broken up by plenty of points. These points will be used for linearization later on.



Now that curve will not be part of the model body... it'll just be floating there.



3: The body volume must be deleted

4: The surface that your curve lies on must be deleted.

5: Split the curves of the old surface where they intersect the datum curve of interest.

6: Create two surfaces where there once was one... plit by the datum curve of interst.

7: Recreate the volume, assign mass props, boundary conditions, loads, etc.



When you look at the meshed model, there should be a distinct curve in
the mesh right along your line and element nodes should line up with
the points on the curve.



If my memory was fuzzy up until this point, it fails me completely
now. Somewhere in here you add the curve or the points or perhaps
you select elements touching the curve... anyway, you use those for
your stress linearization.



Want to teach yourself how to swear a blue streak? After all
this, you run the analysis and can clearly see that you missed or
strayed off the line of high stress and have to go back to step 1!



Sorry I could not be too specific. Perhaps things have become
simpler in the past 7 years. I hope this helps a little.

 

[ghgarzon]

Just a simplistic thought.


Remember that you can mix shells and solids in Pro-Mechanica. Perhaps you can divide the geometry into smaller segments, the simpler ones you model with shells while the more complex one you model as solids; make sure you constrain the rotational degrees of freedom for the shells at the interfaces between solids and shells.


ghgarzon