General Mechanical

General Mechanical

Some questions about stress in PSD

    • Haiquan

      Hello everyone

      I have some questions about stress in PSD

      1. Could we output the principal stress in PSD?
      2. Does the coordinate system of normal stress coincide with global coordinate system in PSD?
      3. For anisotropic material(short fiber reinforced plastics), is X normal stress parallel to global X direction, or is it parallel to the main fiber direction in PSD

      Thank you very much

    • Sean Harvey
      Ansys Employee

      Hello Haiquan,

      Thanks for your inquiry.

      1. No, you can not.  Principal stress does not follow the normal distribution which is the basis of the PSD method.
      2. By default, the stresses in random will be in the solution coordinate system. You will see in the details it says solution coordinate system.

      For solids, this defaults to the global, but for shells, and is on an element-per-element basis (x and y have to be inplane of the shell), so you should use an element orientation (right-click on geometry) branch to specify the orientation.  You can then insert a results object under Results >Coordinate System > Element Triads to visualize the directions.  There is a good write up in the help on this. Solution Coordinate System (

      3. For layered sections in Mechanical the results are also in the solution coordinate system which is the layered direction  (fiber/matrix), but in your case, you have short fiber.  Are you using the short fiber workflow?  Can you confirm back. If so, I will have to double-check.

      Thank you

    • Haiquan

      Hello Sean 

      Thank you very much for your detailed explanations. 
      I use following workflow to input the mesh file and fiber orientation tensor file which are obtained from Moldflow simulation for the short fiber reinforced plastics. My simulation used solid elements with ANSYS 2021 R1
      Question: Is the X axis normal stress parallel to main fiber direction in the element for such case of short fiber reinforced plastics?

      Thank you in advance


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