How the yield stress is calculated from the stress and strain curve imported in Simsolid

KF_001

To perform the non-linear structural analysis for some specific material, I imported the stress and strain curve on the material properties window. Then, the elastic modulus and the yield stress are automatically calculated from the curve imported. After the curve is imported, I can edit the elastic modulus, but cannot edit the yield stress. If the yield stress calculated from the curve is not what I expected, I have no idea of how the curve should be modified.

I would appreciate it if somebody could tell me how the yield stress is calculated from the curve or how the curve should be modified to get the expecting yield stress.

rdominguez

Hello!

Thank you for your question regarding the material properties and stress-strain curve in your non-linear structural analysis. Defining mechanical properties through a stress-strain curve can indeed be a bit tricky, so I’d be happy to provide some clarification.

When you import a stress-strain curve, certain key parameters, such as the Elastic Modulus (Young’s Modulus) and Yield Stress, are derived directly from the data points you provide in the curve. Here’s how these values are typically calculated:

1. First Line of the Curve (0,0): The first point on your stress-strain curve is recommended to be at (0, 0) to define the origin and the beginning of the curve.

2. Second Line of the Curve: The second data point on your curve is crucial as it defines both the Young’s Modulus and the Yield Stress:

   • Elastic Modulus (Young’s Modulus): This is calculated as the slope of the initial (linear) portion of the stress-strain curve. Specifically, it is the ratio of the engineering stress to the corresponding engineering strain at this point.
   • Yield Stress: The engineering stress value from the second point in the curve is interpreted as the yield stress, marking the transition from elastic to plastic deformation.

If the automatically calculated yield stress does not match your expectations, you can adjust the second point in the curve. I recommend setting your desired yield stress as the engineering stress value at this second point. To achieve the correct Young’s Modulus, you can adjust the corresponding engineering strain using a proportion (rule-of-three) based on the desired Elastic Modulus.

Please try this adjustment and let me know if it resolves the issue. If you have any further questions or need additional assistance, feel free to reach out.

KF_001

Thank you so much for your clarification!

I understand that the second point is important in defining both the yield stress and the elastic modulus. I set the second point as yield point and found that the properties became what I expected.

Thank you again,