2 Replies Latest reply on Sep 3, 2009 12:53 PM by Stefan Wozniak

    Worst Case Stress is confusing in a Mixed Mesh problem

      From what I understand...

       

      The "Worst Case Stress"  in a beam analysis the software calculates the highest stress at a critical point on the cross-section by combines the axial and bending stresses due to moments M1 and M2.

       

      In a beam only model - the worst case stress does a good job of calculating the absolute value of the axial stress, bending dir 1, and bending dir 2.

      This value is ALWAYS positive for all elements.

      Ill give an example:

       

      For element # 300:

      Axial Stress = -500 psi

      Bending Stress 1 = -20,000 psi

      Bending Stress 2 = +2500 psi

      Worst Case Stress = |-500| + |-20,000| + 2500 = 23,000 psi

       

      In a mixed mesh model (beam and shell) -  I have placed an shell part in the model (this part has no impact on element 300).  I am confused.  I have worst case stress values that are negative.  Even if I have an insignificant shell part in the model, the Worst Case Stress scale is now in the negative region.

       

      For element # 300:

      Axial Stress = -500 psi

      Bending Stress 1 = -20,000 psi

      Bending Stress 2 = +2500 psi

      Worst Case Stress = -500 + -20,000 + (-1) * 2500 = -23,000 psi

       

      Can someone help with what is going on here?