Difference in average stress values between Mechanical and ACT

Pernelle Marone-Hitz

The averaged Von Mises and principal stress results from Mechanical UI are different to the averaged Von Mises and principal stress values obtained through ACT with stress = reader.GetResult("PRIN_S") and ResultAveragingEnum.Average option, why is that?

Pernelle Marone-Hitz

This is due to the order in which the following operations are performed:

• calculating Von Mises and principal stresses
• averaging the values.

Further explanations can be found here:

• https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v202/en/wb_sim/ds_Unaveraged_Results.html?q=average
• https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v202/en/ans_cmd/Hlp_C_AVPRIN.html

In Mechanical, we:

1. Average the component (X, Y, Z, XY, YZ, XZ) stress values from the elements at a common node.
2. Calculate the Von Mises stress (or principal stresses) from the averaged component values. This is similar to using AVPRIN,0 in Mechanical APDL.

Through ACT scripting, with stress = reader.GetResult("PRIN_S"), we:

1. Calculate the unaveraged principal and Von Mises stresses
2. Average the values if user selects ResultAveragingEnum.Average option in the custom result. This is similar to using AVPRIN,1 in Mechanical APDL.