Reno Genest
Ansys Employee

Hello Mehdi,

What is important are the material directions "a", "b", and "c" and not the element direction. In your case, the material direction is independant of the element direction because of the AOPT option you selected. Here is an example:

In the image above, the material direction shows the "a" direction as defined  by the AOPT option. Note that you can set AOPT= to a negative number and the number represent a local coordinate system ID. The material directions a, b, and c will be aligned with the local coordinate system axis x, y, z.

The element direction is the direction from node 1 to node 2 as defined on the *ELEMENT_SOLID card. For the solid element 88 in the image above, node 1 is node # 128 and node 2 is node # 137 and so the element direction is from node 128 to node 137:


But, the element direction does not matter here; what is important are the material directions "a", "b", and "c". 

For a regular  orthotropic material model, for example *MAT_002, the material directions for Young's moduli and other constants are clearly labeled:

So, the Young's modulu Ea  is in the material "a" direction for all element.

In the case of *MAT_WOOD, the parallel direction is the same as the material direction "a" and the perpendicular direction is material directions "b", and "c".

You will find more information about material directions and element directions in the following pdf:


So, in your case, if the material direction "a" is aligned with the global Z axis, then the parallel direction in *MAT_WOOD correspond to the material direction "a" and global Z axis.


I hope this helps.