General Mechanical

General Mechanical

Can’t Curve fit some hyperelastic material models

    • Lovisa Svanborg
      Subscriber

      Hi!

      I am doing curve fitt of hyperelastic material model. But when I choose Ogden and Gent model, it curve fit the plot but will not show constants and error in table. It doesn't change, it says just values 0 an 1. So I want to see the values for these models as well. Why can't the parameters change?

      Regards

    • Vinayak Vipradas
      Ansys Employee

      Hi Lovisa, 

      Please refer to the following links:

      Mechanical Material Curve Fitting (ansys.com) 
      6.1. Hyperelastic Material Curve-Fitting (ansys.com)

       

      Thanks,
      Vinayak 

       

    • Lovisa Svanborg
      Subscriber

      Thanks!

      Sorry I dont have account registration and I account number.

      Lovisa

    • Vinayak Vipradas
      Ansys Employee

      You need to create an account if you don't already have one to access the Ansys Help website. 

      Thanks, 
      Vinayak

    • Lovisa Svanborg
      Subscriber

      Now a account is fixed.

      Still a don't know how to quess the initial values of the coefficients for nonlinear regression for hyperelastic material models.

      Lovisa

       

    • Vinayak Vipradas
      Ansys Employee

      The initial values of the coefficients can come from examining the function that defines the model to which you are attempting to compare/fit your data. For most hyperelastic models, 1 or -1 is a good starting point; however, coefficient values can vary greatly depending on the model chosen. The Gent model, for example, provides good fit with initial coefficient values as high as 1000.

      For further information, please refer to the following link: 

      https://ansyshelp.ansys.com/Views/Secured/corp/v222/en/ans_mat/Hlp_G_STRmcfhyp.html#hmcfinitialize 

    • Lovisa Svanborg
      Subscriber

      Ok, thanks! I find now in ansys values of coficients and errors. It says you can generate the initial values of the coefficients automatically, and also that the initial values of the coefficients can also come from experience. So I can just go for automatically, why change? Can it be better. If I use automatically, what is the difference between curve fit for linear and nonlinear regression. I just solve for curve fit and can see the values.

      Lovisa

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