I received the following question via email:
I am a little confused about how to deal with Ramberg Osgood stress strain curves when trying to set up a curve for moment versus edge strain and I have a similar problem with Torsion. Is it possible to break the Ramberg Osgood curve into an elastic section and a power hardening section, or does equation13.27 (the one with Beta's) have to be used? If equation 13.27 is the right way to go, how is it possible to eliminate yield stress from the equation and make the expression a function of edge strain?
You don't have to have an explicit equation to make the plot. You have eq 13.27 relating M to edge stress, and then you have the ramberg-osgood equation, which you can use to calculate edge strain from edge stress.
-- Dr. VanLandingham