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Registered: ‎08-18-2013

Internal Pressure of 0.5MPA in Midplane Meshed Cylinder Part 2

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09-28-2013 08:03 PM

Hello all!!!

 

I've attached a sample mid-plane meshed file. Basically my question is how can i properly input an internal pressure of 0.5Mpa to get reasonable value. What I'm getting is actually 2052 Mpa Von Mises Stress. In a solid model this is only 127Mpa which compares well with another FEA software using shell element which has a result of 118 MPa. Actually if the result in the torsional moment is comparing well with using solid element, I would stick with using solid element to solve the elbow problem. Basically if I combine the internal pressure load and moment loads I'm getting a difference of around 50MPa b/w plate/shell vs solid element (with plate/shell value of 230Mpa vs solid of 180Mpa).

 

I'm having no problem in moments and forces applied to mid-plane meshed model. It's only in internal pressure that I can't figure out to get the proper input to have a reasonable output.

 

Cheers to all FEA'rs!!!!

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Re: Internal Pressure of 0.5MPA in Midplane Meshed Cylinder Part 2

09-29-2013 12:06 AM in reply to: tibor121774

I think I've found the problem. The direction of element axis 3 for the surface are not on one direction (they are opposite and counteracting each other causing maybe large bending moment in the system). The only problem now is how I will define the pressure for each element in the proper direction. Hope someone there have an idea.....Many thanks in advance....

 

Cheers to all!!!!

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Registered: ‎08-18-2013

Re: Internal Pressure of 0.5MPA in Midplane Meshed Cylinder Part 2

09-29-2013 12:06 AM in reply to: tibor121774

I think I've found the problem. The direction of element axis 3 for the surface are not on one direction (they are opposite and counteracting each other causing maybe large bending moment in the system). The only problem now is how I will define the pressure for each element in the proper direction. Hope someone there have an idea.....Many thanks in advance....

 

Cheers to all!!!!

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Registered: ‎08-30-2012

Re: Internal Pressure of 0.5MPA in Midplane Meshed Cylinder Part 2

09-30-2013 05:52 PM in reply to: tibor121774

Hi tibor,

 

I guess my reply in the previous thread (http://forums.autodesk.com/t5/Autodesk-Simulation-Mechanical/Internal-Pressure-of-0-5MPA-in-Midplane...) did not answer all of your questions. :smileysad:

 

I have attached an archive of a model that may help to visualize the solution. Change the extension to .ACH after downloading the .zip file, and open it with Simulation Mechanical.

 

Parts 1, 2, and 3 are a replica of your model. (See the image "parts 1 2 3 the model.png" attached.)  I used different part numbers only to make it easier to hide parts as needed. If you extend the straight pipes (make parts 11 and 13 visible) and split them (hide part 2, show part 12 the elbow), there is a volume of space shared by all three parts. (See "parts 11 12 13 the intersection volumes.png".) If you enter the Element Normal Coordinate in the Element Definition somewhere within this volume, then the "bottom" of the plate elements will be what you and I consider the inside of the pipes. Take a look at the element 3 axis in the Results environment.

 

It is a little easier to visualize this in the software because you can rotate the model around. It is even easier to visualize if you make a solid model in Fusion or Inventor (that is, solid bars instead of pipes) and create the "intersection" of the pieces and leave just the common intersection (union) of them.

 

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

Simulation Mechanical user since Dec 1997
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Re: Internal Pressure of 0.5MPA in Midplane Meshed Cylinder Part 2

10-03-2013 08:31 AM in reply to: tibor121774

Thanks a lot John....That does the trick.....