| SX |
X normal stress |
| SY |
Y normal stress |
| SZ |
Z normal stress |
| TXY |
Shear in Y direction on YZ plane |
| TXZ |
Shear in Z direction on YZ plane |
| TYZ |
Shear in Z direction on XZ plane |
The following quantities do not use reference geometry:
| P1 |
1st principal stress (largest) |
| P2 |
2nd principal stress |
| P3 |
3rd principal stress |
| VON |
von Mises stress |
| INT |
Stress intensity = P1 - P3 |
| ERR |
Energy Norm Error (available for element stresses only) |
| CP |
Contact pressure |
Principal Stresses
Stress components depend on the directions in which they are calculated. For certain coordinate axis rotations, shear stresses vanish. The remaining three normal stress components are called principal stresses. The directions associated with principal stresses are called the principal directions.
Von Mises or Equivalent Stresses
Unlike stress components, the von Mises stress has no direction. It is fully defined by magnitude with stress units. The von Mises stress is used by failure criteria to assess failure of ductile materials.
The von Mises stress is computed from the six stress components as follows:
VON = {0.5 [(SX -SY)2 + (SX-SZ)2 + (SY-SZ)2] + 3(TXY2 + TXZ2 + TYZ2)}(1/2)
Or equivalently, from the three principal stresses,
VON = {0.5 [(P1 - P2)2 + (P1 - P3)2 + (P2 - P3)2]}(1/2)