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
John Holtz, P.E. Global Product Support
Autodesk, Inc. If not provided already, be sure to indicate the version of Inventor Nastran you are using!"The knowledge you seek is at knowledge.autodesk.com" - Confucius 😉