Maximum Shear Stress Criterion
The maximum shear stress criterion, also known as Tresca yield criterion,
is based on the Maximum Shear stress theory.
This theory predicts failure of a material to occur when the absolute
maximum shear stress (tmax)
reaches the stress that causes the material to yield in a simple tension
test. The Maximum shear stress criterion is used for ductile
materials.
tmax
≥ slimit/
2
tmax
is the greatest of t12,
t23and
t13
Where:
t12 = (s1 - s2)/2; t23 = (s2- s3)/2; t13 = (s1- s3)/2
Hence:
Factor of safety (FOS)
= slimit /(2*tmax)
Comparing the von Mises and Tresca Stress Criteria
The maximum shear stress criterion is more conservative than the von
Mises stress criterion since the hexagon representing the shear stress
criterion is enclosed within the ellipse representing the von Mises stress
criterion.
For a condition of pure shear, von Mises stress criterion predicts failure
at (0.577*yield strength) whereas the shear stress criterion predicts
failure at 0.5 yield strength. Actual torsion tests used to develop pure
shear have shown that the von Mises stress criterion gives more accurate
results than the maximum shear stress theory.
Related Topics
Performing
factor of safety check