I would like to inform the fracture mechanics community of an asymptotic solution for the steady-state mode I crack problem for an elastic / perfectly plastic material under plane stress loading conditons. See the following article in ZAMP, i.e.,
Students often have a tough time understanding the crack driving force in an elementary course on fracture mechanics.
A recent free access article has been published on a fluid analogy to the crack driving force and the Riabouchinsky free streamline problem for ideal fluid flow around two plates. Hopefully this analogy can aid in the visualization.
The URL where this article can be downloaded is found at 10.1515/jmbm-2019-0011
My text, Analytical Fracture Mechanics, is back in print by Dover Publications as of November 2011.