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Nastran Shell Element Orientation Question


This isn't exactly related to FEMAP, but a more general Nastran question.


I thought I had nailed the understanding but I was watching a couple of Femap videos and now I am questioning my understanding.


Wanted to get a clear picture on how Shell top, bottom, Face 1,2, Z1 & Z2 are represented with respect to Element Normal. The current understanding I have is as follows:


Untitled 1.png

Is the above accurate?




Re: Nastran Shell Element Orientation Question

Siemens Phenom Siemens Phenom
Siemens Phenom

In  your picture, you have the element normal reversed as Face 1 is the top face of Nastran shell element.


I hope the snapshot below will help where the element cordinate system is shown as Red = X, Green = Y and Blue = Z.  The black arrow indicates the element normal direction.





Another way to understand this is to turn on element thickness display and with the option for Pick Front enable, choose a command such as Mesh > Extrude > Element Face and when you select a face, it will show what element face you've selected in the Select Element Faces dialog box.


A good source of information on elements is the Nastran Element Reference Guide accessible by clicking the Help > NX Nastran command and select Element Library Reference under the Reference Guides section. 

Best Regards,
Chip Fricke
Principal Applications Engineer - Femap Product Development

Re: Nastran Shell Element Orientation Question


Thanks for replying.


I did a simple surface meshed with plate elements, with one end of the surface fixed and a transverse load applied to the other end. Bascially subjected the plate to bending and verified the orientation of top, bottom, Z1, Z2 (for MSC users), Face 1 & Face 2. 


I am just posting the updated illustration of all of the above relative to Shell Normal Vector.




Re: Nastran Shell Element Orientation Question


Your diagram is now correct.  

FYI, Z1 and Z2 are also applicable to NX Nastran users.  You can adjust Z1 and Z2 from the Nastran defaults ( Z1 = -T/2 and Z2 = +T/2) in Femap by editing the plate property and entering values for the Bottom Fibre (Z1) and the Top Fibre (Z2) to specify alternate stress recovery locations to the obvious defaults.

To see the details, refer to the "PSHELL" (plate property) entry in the [NX or MSC] Nastran Quick Reference Guide mentioned by Chip.