MAKE-FEM bug?

[ChaliBiky]

simulation multiphisics2012

I'm checking a pressured membrane.

The attached figure B shows an analysis result of a pressured dome-shaped membrane, which

is derived from figure A using Make FEM command.

Looking B, you'll notice the orientation of some meshed segments are reversed: some

pressure arrows direct wrong.

Is this a bug of MAKE-FEM? How can I fix this problem by manual? how to reverse some arrows?

[John_Holtz]

Hi Chalibiky,

It is difficult to know where the problem lies without having the model. The items I suggest checking in model B are the surface number of the lines and the location of the element normal coordinate. These can be checked in the FEA Editor from the "View > Appearance > Color By > Surface" and the part's Element Definition, respectively.

The Make FEM command ("Results Options > Other > Tools > Make FEM") needs to make assumptions or use default values for some of the input, so I think you simply need to update that information to make the new model correct.

[ChaliBiky]

Thank you for your reply.

 By the way I modeled A with 4 points structured mesh,using divisions number=4 for both sides.

 According to your suggestion, I selected Model B and changed surface number = 2 , but nothing has

changed.

Now I traced model B facets with 4 points structred mesh with divisions number=1 for both sides

one by one each clockwisely, making model C. This is very time consuming but no way due to your

bugs. Selecting model C all and add pressure and run to see the same wrong results.

could you explain this?

Regards,

 ChaliBiky

[John_Holtz · Accepted solution]

User error.

Under the Element Definition, on the Orientation tab, you need to enter the Element Normal coordinate so that it is a point "underneath" the structure. For example, (0, 0, -500) mm.

To understand why the input was incorrect, click the Help button on the Element Definition dialog, then scroll down the page to the section "Control Orientation Membrane Elements > Element Axes". Essentially, each individual element is like a sheet of paper. You applied a pressure to the paper, but where did you tell the software which side of the paper you wanted the pressure? That is what the Element Normal coordinate is for.