Maximum von Mises Stress Criterion
The
maximum von Mises stress criterion is based on the von Mises-Hencky
theory, also known as the Shear-energy theory or the Maximum distortion
energy theory.
In terms of the principal stresses s1,
s2,
and s3,
the von Mises stress is expressed as:
svonMises
= {[(s1
- s2)2 + (s2 - s3)2
+ (s1
- s3)2]/2}(1/2)
The theory states that a ductile
material starts to yield at a location when the von Mises stress becomes
equal to the stress limit. In most cases, the yield strength is used as
the stress limit. However, the software allows you to use the ultimate
tensile or set your own stress limit.
svonMises
≥ slimit
Yield strength is a temperature-dependent
property. This specified value of the yield strength should consider the
temperature of the component. The factor of safety at a location is calculated
from:
Factor of Safety (FOS)
= slimit
/ svonMises
Pure Shear
In the case of pure shear t,
von Mises stress can be expressed as:
svonMises
= (3)1/2 t
Failure occurs if:
tmax
= 0.577 syield
Related Topics
Performing
factor of safety check