[rda2]

For those who are interested in learning more:

"All failure is shear failure" - this is a simple explanation of Tresca's Yield Criterion. For materials with higher compressive than tensile strength, the equivalent is the Mohr-Coulomb failure criterion.

https://en.wikipedia.org/wiki/Material_failure_theory

[kurthr]

For a simple example try twisting a ductile aluminum bolt (or clay), twisting a brittle piece of chalk (or concrete), or twisting a composite (twig). They all fail differently (and the first two at 45deg to each other. Mohr's circle is interesting, and fatigue failure more interesting still.

https://youtu.be/1YTKedLQOa0?t=533