The following table summarizes the failure criteria used to assess the safety of designs.
| Criterion |
Factor of Safety |
Material Type |
|---|
| Maximum von Mises stress
|
σlimit / σvonMises |
Ductile
|
| Maximum shear stress
|
σ limit / (2 * τmax ) |
Ductile
|
| Mohr-Coulomb stress
|
If ( σ1> 0 and σ3 > 0 ) then ( σ1 ≥ σTensileLimit )
If ( σ1< 0 and σ3 < 0 ) then ( σ3 ≥ -σCompressiveLimit )
- If ( σ1≥ 0 and σ3 ≤ 0 ) then ( σ1 / σTensileLimit + σ3 / -σCompressiveLimit ≥1 )
|
Brittle materials with different tensile and compressive strengths
|
| Maximum normal stress
|
σ limit / 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
|