pulling yield stress automatically

Hello,

I have some stress strain data from a tensile test. This is a typical looking stress strain curve. I am trying to figure out a way with matlab to pull the yield stress automatically. The yield strength is simply the .02% offset using the elastic range slope. I am sure someone has done this before. Any help would be great.

[dpb]

Probably a toughie unless the data are very clean (w/o noise, scatter, etc.)

Best guess w/o any data to actually play with might be to start w/ a linear fit on the left adding points until the goodness of fit begins to degrade. Of course, if it's noisy it may be quite a ways past the first curvature point before there's enough variation to pick it out...

I'd suppose there would be literature in the field one should be able to find...