[ngoc_tran_bao]

Dear all friends,
My problem relates to the simulation using Ansys ACP and Static Structural.
I carry out a simulation for a box structure analysis, the material layup for the composite material is created in ACP and the structure analysis is conducted in Ansys Static Structural.
My target is to evaluate the behaviour of the box under external forces according to some failure criterion.
The expression for failure criteria is:
((SXY/(2*(1+0.25)*60))^2 + (SY/100)^2)*100/SY
where SXY is the shear stress in XY plane;
SY is the stress in Y direction;
During the simulation, I confuse when selecting the coordinate for "user-defined results": Global Coordinate or Local Coordinate?
The Local Coordinate (Rosette) is defined in Ansys ACP when creating the layup arrangement. For this coordinate, X-direction is set as a reference direction for composite material.
In the Structure simulation, I get two different calculation results when selecting two different coordinates for expression evaluation and I don't know which result is correct.
Can you please help me to make it clear that when I should you Local Coordinate or Global Coordinate?
Thank you for your time.