How to write a C++ class header file for Yeoh model based on the existing hyperelastic material model

[hyzhao955]

Hi SOFA,

I am new with SOFA and trying to write a C++ class header file for Yeoh model due to our research need. However, I am not sure what should be covered in "applyElasticityTensor()" in my header file. Could you explain more about this method in existing models. For example in Neo-hookean model as attached in code box, what the symbol "H" represent for ? What the "input tensor" and "output tensor" represent for? Where is the formula for computing the output tensor come from?
Looking forward to receiving your reply, thanks.@hugtalbot

    void applyElasticityTensor(StrainInformation<DataTypes>* sinfo,
                               const MaterialParameters<DataTypes>& param,
                               const MatrixSym& inputTensor, MatrixSym& outputTensor) override
    {
        Real mu = param.parameterArray[0];
        Real k = param.parameterArray[1];
        MatrixSym inversematrix;
        invertMatrix(inversematrix, sinfo->deformationTensor);
        MatrixSym ID;
        ID.identity();
        Real trHC = inputTensor[0]*inversematrix[0]+inputTensor[2]*inversematrix[2]+inputTensor[5]*
                    inversematrix[5]
                    +2*inputTensor[1]*inversematrix[1]+2*inputTensor[3]*inversematrix[3]+2*
                    inputTensor[4]*inversematrix[4];
        MatrixSym Firstmatrix;
        Firstmatrix.Mat2Sym(inversematrix.SymMatMultiply(inputTensor.SymSymMultiply(inversematrix)),
                            Firstmatrix);
        outputTensor = Firstmatrix*(mu-k*log(sinfo->J))+inversematrix*(k*trHC/2);
    }

[hugtalbot]

Hi @hyzhao955

So sorry for the delayed answer but the organization of the SOFA Week 2023 kept us busy!

Nice to see that you would like to write a Yeoh model. It can be implemented within the material folder or within the Caribou plugin (plugin for modular continuum mechanics).

The applyElasticityTensor() is a function which computes the elasticity tensor of the current configuration. In the case of the STVenantKirchhoff material we can read:

outputTensor = ID*trH*lambda/2.0+inputTensor*mu;

where the outputTensor multiplies an input one with the material coefficient (included in this elasticity tensor).

Does this clarifies it?

[github-actions[bot]]

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@hyzhao955
Feedback has been given to you by the project reviewers, however we have not received a response from you. Without further news in the coming weeks, this discussion will be automatically closed in order to keep this forum clean and fresh 🌱 Thank you for your understanding

[github-actions[bot]]

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@hyzhao955
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