Si Hwa Heng In the scenario you described, where the yield limit is beyond the proportional limit, you can define the yield point in ABAQUS using an offset yield approach. First define the elastic behavior up to the proportional limit (Point A) using the elastic modulus. Then for the plastic behavior beyond the proportional limit, use an offset yield approach to define the yield point. The offset yield point is an arbitrary point on the stress-strain curve that represents the onset of significant plastic deformation. The most common offset is 0.2%, meaning the yield point is defined as the stress at which 0.2% plastic strain occurs. Determine the 0.2% offset yield stress (Point B). This is the stress value on the stress-strain curve at 0.2% plastic strain. In the ABAQUS material definition, specify the elastic behavior up to the proportional limit (Point A) using the elastic modulus. For the plastic behavior, define the yield stress using the 0.2% offset yield stress (Point B). This will allow you to capture the plastic deformation behavior beyond the proportional limit, without losing stiffness in the elastic region. I will recommend you to get the curve and process it using MCalibration software and then use the processed curve and parameter in ABAQUS.

Hi Engr. Tufail,

Many thanks for your reply, but I am still a little confused as to how this is defined in ABAQUS.

I have attached 2 pictures taken from ABAQUS property module: One for the elastic properties, and the other for plastic properties. If I have a steel with a proportional limit at a stress level of 355MPa and yield limit of 370MPa with E = 210000MPa. Is the below how I will do it? How do I define the slope between the proportional limit and yield limit then?

My problem is the stress-strain (SS) curve before the yield point (i.e. before permanent deformation occurs) is not linear. To the best of my knowledge, ABAQUS only let you define linear SS response up to the yield limit through the E value and the first entry on the plastic properties table, however, I have a non-linear SS response up to the yield limit.

Many thanks,

Heng

For such cases, draw a line parallel to initial tangent of stress-strain curve from 0.2% strain (proof strain) and where it touches your stress strain curve, mark it as yield strength. Forget about difference between experimental observation of proportionality limit and yield limit.

That's the most authentic method to be used for metals like Aluminum, that doesn't have defined yield point.

Thanks Narayan,

So basically just assume the nonlinearity between the proportional limit and yield limit as linear by shifting the initial tangent 0.2% strain forward.

Thanks Narayan .. & Engr. Tufail

To some extent, Yes !