| Maximum von Mises stress
|
σlimit / σvonMises |
Ductile
|
| Maximum shear stress
|
σlimit / (2 * τmax) |
Ductile
|
| Mohr-Coulomb stress
|
- σ1 > σ 2 >
σ3,
If (σ1> 0 and σ3 > 0)
then (σ1 ≥ σTensile Limit)
If (σ1< 0 and σ3 < 0)
then (|σ3| ≥ σCompressive Limit)
- If (σ1> 0 and σ3 <0)
then (σ1 / σTensile Limit + |σ3| / σCompressive Limit ≥1)
When the third principal stress σ3 is in compression
(negative), both values for σ3 and the material's compressive limit have
positive signs for the FOS
calculation.
|
Brittle materials with different tensile and compressive strengths
|
| Maximum normal stress
|
σlimit / σ1 |
Brittle
|
| Maximum stress criterion (composites)
|
 FOS = 1/F.I.
|
Brittle
1 and 2 stand for material directions. X and S are normal and shear strengths of the composite.
|
| Tsai-Hill Failure criterion (composites) |
 FOS = 1 / SQRT (F.I.)
|
Brittle
|
| Tsai-Wu Failure criterion (composites)
|
|
Brittle
|