How can I automatically extract stress along the boundaries in mechanical stress calculations?

Hi all,

I have plain stress problem, in which I need to access the von Mises stress along the edges/boundaries within an iterative algorithm. I have written a script moving through all mesh triangle, checking whether their edges lie on the edges and can robustly extract stress along the edges this way. However, the script is very slow. Does anyone know of an existing script, or has a suggestion for a better solution?

Thanks, JMT