General Mechanical

General Mechanical

Curve fit hyperelastic – Stable or unstable model

    • Lovisa Svanborg


      I wonder if I just have biaxial data and do curve fit, is the model unstable if the resul looks like this:

      The model is stable for biaxial but not for the other modes. For just using one data test should all modes be stable or do I just look at the biaxial?

      Regards Lovisa

    • Mike Rife
      Ansys Employee

      Hi Lovisa Svanborg

      I think you answered your own question.  The material model is not stable as the uniaxial response turns negative at strain ~0.125 and would likely have solution difficulty before that.  But, do you expect uniaxial strains larger than say 0.05?  If not then you could probably use this fit.  Otherwise I'd redo the fit changing the options...maybe use a different hyperelastic material model.


    • SaiD
      Ansys Employee


      You may find this video helpful: How to Perform Curve-fitting for Hyperelastic Material Models — Lesson 1 - ANSYS Innovation Courses

      Watch the video at around 3:10. If you only have Biaxial data, then material response in only that mode of deformation may be considered reliable. Material response in other modes may not be as reliable. So if your model deforms only in the biaxial load, this data set might be sufficient. But if it deforms in other modes, you need more data to caliberate your hyperelastic material model and to get sufficiently reliable results in your simulation.

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