von Mises stress is an equivalent stress. More precisely, it is the stress associated with the von Mises failure criterion for ductile materials.
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. 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.
von Mises stress can be expressed in various ways, and there are some special cases of von Mises stress as shown in the table below.
[1]https://en.wikipedia.org/wiki/Von_Mises_yield_criterion
Also read a comparison between failure criteria.
This page is part of The Encyclopedia of Stresses in Solids