Creation of a stress-strain curve for FE analysis with the Ramberg-Osgood Equation

Ramberg-Osgood Equation - Describes the nonlinear relationship between stress and strain. It is special applicable to metals that harden under plastic deformation.
This relationship was proposed to describe the stress-strain curve using three parameters by Walter Ramberg and William R. Osgood from National Advisory Committee for Aeronautics, 1943.
Excel tool to create a stress-strain curve:
docs.google.co...
References
- Ramberg, W., & Osgood, W. R. (1943). Description of stress-strain curves by three parameters. Technical Note No. 902, National Advisory Committee For Aeronautics, Washington DC; ntrs.nasa.gov/...
- Getting Started with ABAQUS 10.2 Plasticity in ductile metals

[@alcidesgarcia7118]

Master Andrea, sincerely grateful to you. Few people share information, but you, for example, share. Thank you.

[@Gonzanoza]

Thank you so much!

[@alcidesgarcia7118]

Master Andrea, I congratulate you for the tutorial and the explanation in this one. Please, can you tell me that, once I do the stress-strain curve approximation: Ramber-Osgood, what value I should take as a coefficient since I define the value of n (exponent) prior to analyzing the curve.

[@alcidesgarcia7118]

Excuse me, I clarify, these data, n-exponent and K-coefficient, are taken in the offpipe and orca flex programs. I want to know, if you guide me, on the graph, what coefficient value I should take.

[@andreas-baer-engineering]

Hi Alcides Garcia,
in OrcaFlex the relationship between stress and strain can be specified using either Ramberg-Osgood or a stress-strain table.
You can use my Excel tool to define the stress-strain table or you can convert to Ramberg-Osgood using the parameters K and n (K, n - constants that depend on the material).
For K, n you need two equations. Example S355, two points from the curve:
Point 1 with stress = 355 and strain_eng=0.00369
Point 2 with stress = 470; strain_eng = 0.2
Formula [1] from point 1: 0.00369 = 355/210000 + K*(355/210000)^n
Formula [1] from point 2: 0.2 = 470/210000 + K*(470/210000)^n
Isolate K and solve n >>> n = ln 0.01011 / ln 0.7553191 = 16.37089
then with formula from point 1 or point 2 >>> K = 4.79731E+42
After you can then compare curves - for further details see Excel:
docs.google.com/spreadsheets/d/1RVna6O0ZFjtK8PN_rqyjKN34XVOzXWAs/edit?usp=sharing&ouid=106721331533058990532&rtpof=true&sd=true