Von Mises Equivalent Strain

Entity name: Mises

\begin{displaymath}\epsilon_{vM} = 2/3 * \frac{1}{\sqrt{2}} \sqrt{(\epsilon_{x}-\epsilon_{y})^{2}+(\epsilon_{y}-\epsilon_{z})^{2}+(\epsilon_{z}-\epsilon_{x})^{2}+6\epsilon_{yz}^{2}+6\epsilon_{zx}^{2}+6\epsilon_{xy}^{2}}\end{displaymath}