Material orientation (e.g. on shell elements like CTRIA or CQUAD) exists and
can be displayed,
even though user hasn't set anything related to it.
Solution
This is by design.
If we see inside the mesh associated data, we'll find that by default the
Material Orientation Method is set to "Orientation Angle". And since no value
has been set, zero will be used to determine the direction, which means it is
aligned with the x-axis.
This is in accordance e.g. with the CTRIA3 format definition from the online
help.
/>https://docs.plm.automation.siemens.com/tdoc/nx/11.0.2/nx_help/#uid:id489311
The definition of the method "orientation angle" can be found here:
/>https://docs.plm.automation.siemens.com/tdoc/nx/11.0.1/nx_help#uid:id629876
"Orientation Angle - Specify an angle. The software orients the X-axis of the
material coordinate system using the specified angle from the first edge of
the element."
The first edge of the element is referring to the edge that is constructed
from the first two nodes that are listed on NX-Nastran code. On NX, we can
display this using "Solver Syntax Preview":
Take for example this CTRIA3 element nr. 414:
$TRIA3 EID PID G1 G2 G3
CTRIA3 414 1 316 315 314
The vector that is formed from node 316 to node 315 defines the material
orientation for this tria element.
Notes