Hi all,
I recently did a coupon test on my S355 steel and wanted to calculate the yield strength from the stress-strain plot I am getting. The plot I have does not have a distinct yield point (i.e. curve around the yield), so I am looking to calculate the 0.2% offset yield strength (or 0.2% proof strength, as some may call).
From the code, there was a line that says "Proof strength, non-proportional extension (Rp)" [See attached graph from EN 10002-1 for reference]. Does anyone know what the term "non-proportional extension" means? Does it simply mean any test that doesn't have a distinct peak?
Also, what is meant by a proportional test piece and what is a non-proportional test piece?
Many thanks,
Heng
Non-proportional extension means that - at some point - the deformations (strain) increase at a higher rate than the load (stress). Below that point/region there is a linear relationship between load and deformation (stress and strain).
