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
|
s
limit
/
s
vonMises
|
Ductile
|
|
Maximum shear stress
|
slimit /(2*tmax)
|
Ductile
|
|
Mohr-Coulomb stress
|
s
1 ≥
s
TensileLimit
if s
1 > 0 and s
3 > 0
s
3 ≥ -
s
CompressiveLimit
if s
1 < 0 and s
3 < 0
{
s
1 /
s
TensileLimit
+ s
3
/
s
CompressiveLimit
}
(-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)
|
|
Brittle
|
|
Tsai-Wu Failure criterion (composites)
|
|
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.