The element has two coordinate systems associated with it, the element system and the material system. The element system is defined by the geometry of the element and is fixed, for reference see the entry in the quick reference guide(qrg). The material system you can define and in Patran you do this through the "properties".
A couple of pictures to illustrate. Note that the material system x,y lie in the element plane so their direction is obtained by a projection of the material reference coordinate system into the element plane. ref qrg.
The pictures illustrate use of a CID and a vector to define the material direction.
Hi Arthur,
What I’m really trying to do is align the first edge of a quad or tri element (direction of node 1 to 2 and thus the element coordinate system) with a user defined coordinate system X axis.
Thanks so much for your time
OK, sorry I was trying to do the "exact" orientation.
For the element topology alignment you can use the utility found under:
Utilities / FEM-Elements / Modify Element Orientation ...
this will modify the node order and you probably want :
Target : Quads Tris
Method: Vector Match
and then for "Select Vector" use the relevant 1,2 or 3 axis and the coord system you want (e.g. Coord 5.1).
Hopefully that is what you wanted, sorry for not realizing this at first.
By the way, a minor detail but if you are using Nastran note that the Element x axis is the bisector of the angle between the diagonals (n1->3 and n4->2) of the element (in the element plane). For rectangular elements this corresponds to edge 1 (node 1 to 2) but for arbitrarily shaped elements it can be slightly different.
