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Active Member
artugan
Posts: 7
Registered: ‎04-20-2010

Declaring pressure on plate elements

448 Views, 3 Replies
04-24-2010 02:43 AM
I have a problem with declaring pressures on plate/shell elements from models made in AutoCAD. Most of arrows which display direction of pressure are doing it ok but sometimes some of them are showing opposite direction. I am annoyed with this, changing mesh doesn't help. It mostly happens next to connection of different elements. Is it CAD model issue or Algor? I used regions to make plate elements, but now AutoCAD has some surface stuff could it help? or should I use Algor interface to make models? I attached my cad model in dwg to this post. I want to declare pressure on the bottom surface of model (hull bottom frame).
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Active Member
artugan
Posts: 7
Registered: ‎04-20-2010

Re: Declaring pressure on plate elements

04-24-2010 02:46 AM in reply to: artugan
Sorry I uploaded wrong dwg file don't download it.
Also I wanted to post also fem file but i cannot so i give a link to them with GOOD DWG file.
http://wyslijto.pl/plik/pk4gczymij
to download click "plate frame files.zip"
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Employee
INACTIVE_AstroJohn
Posts: 492
Registered: ‎03-25-2010

Re: Declaring pressure on plate elements

04-26-2010 08:40 AM in reply to: artugan
Hi,

Unfortunately, the file you sent (.fem file) does not contain the full input. In the future, you should create an archive of the model ("File > Archive > Create") and provide the .ach file.

But the DXF file may provide the answer. Plates element by themself do not have a clearly defined "top" or "bottom". To the software, one side looks just like the other. So, how did you tell the software to put the pressure on one side instead of the other side? (In comparison, brick elements have a volume, so the software can detect the direction that pushes into the element.)

For plate elements, the user tells the software which side is the bottom of the plate elements in the "Element Definition" dialog (the same place that the thickness is entered). The "Element Normal X, Y, Z" coordinates entered on the "Orientation" tab is a coordinate somewhere off of the part and "below" all of the elements. My guess is that this coordinate is at the default location which just happens to be the plane of the plate that you are loading. Because of roundoff, some of your elements turned out to have the bottom side in the opposite direction from the other elements. Please try entering a Z coordinate of -5.

P.S. I just noticed that two of your plates (parts 2 and 6 when I imported the DWG file) are passing right through each other, so there is no connection between them. You need to intersect the two plates that form the + so that they are connected together.

John Holtz
Product Design Engineer, Algor Simulation
Autodesk, Inc Edited by: AstroJohn on Apr 26, 2010 3:41 PM
Sincerely,
John Holtz, P.E.
Senior User Experience Designer, Simulation
Autodesk, Inc.

Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)
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Active Member
artugan
Posts: 7
Registered: ‎04-20-2010

Re: Declaring pressure on plate elements

04-26-2010 02:29 PM in reply to: artugan
Thank you very much defining normal to surface helped. I simply couldn't find such thing anywhere.
Crossing parts were one of solutions made by me to go around this problem but also did not work.
Again thank you that info solved my problem.
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