Summary of Failure Criteria
The following table summarizes the failure criteria used to assess the
safety of designs.
|
Criterion |
Factor of Safety |
Material Type |
|
Maximum von Mises stress |
slimit / svonMises |
Ductile |
|
Maximum shear stress |
slimit /(2*tmax) |
Ductile |
|
Mohr-Coulomb stress |
s1
≥ sTensileLimit if
s1
> 0 and s3
> 0
s3
≥
- sCompressiveLimit
if s1
< 0
and s3
< 0
{s1
/ sTensileLimit + s3 /
sCompressiveLimit} (-1)
< 1 if
s1
≥ 0 and s3 ≤
0 |
Brittle materials with different tensile and compressive strengths |
|
Maximum normal stress |
slimit /
s1 |
Brittle |
|
Maximum
stress criterion (composites) |
F.O.S.
= 1/F.I. |
Brittle |
|
Tsai-Hill
Failure criterion (composites) |
F.O.S.
= 1/F.I. |
Brittle |
|
Tsai-Wu
Failure criterion (composites) |
F.O.S.
= 1/F.I. |
Brittle |
Click on each of the failure criterion for
composites to know the meaning of the different symbols. 1 and 2 stand
for material directions. X and
S are normal and shear strengths
of the composite.