Stress–Strain Curve

It reproduces the smooth, continuously hardening curves of ductile metals well between yield and ultimate. It will not capture sharp yield points (upper/lower yield of mild steel), Lüders plateaus, or post-necking behaviour — the curve is engineering stress–strain up to the ultimate strength.

That is the standard 0.2% offset definition of yield strength: the yield point is where a line offset by 0.002 strain, parallel to the elastic slope, intersects the curve. The Ramberg–Osgood fit is anchored to it.