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OrthotropicSolid seems to be wrong #680

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WeiyiVirtonomy opened this issue Oct 30, 2024 · 4 comments
Open

OrthotropicSolid seems to be wrong #680

WeiyiVirtonomy opened this issue Oct 30, 2024 · 4 comments

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@WeiyiVirtonomy
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WeiyiVirtonomy commented Oct 30, 2024 •
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The function CalculateAllLambda() defines the compliance matrix as:

    Matd Compliance = Matd::Zero();
    Compliance.col(0) = Vecd(1 / E_[0], -poisson_[0] / E_[1], -poisson_[1] / E_[2]);
    Compliance.col(1) = Vecd(-poisson_[0] / E_[0], 1 / E_[1], -poisson_[2] / E_[1]);
    Compliance.col(2) = Vecd(-poisson_[1] / E_[0], -poisson_[2] / E_[1], 1 / E_[2]);

Shouldn't it be

    Matd Compliance = Matd::Zero();
    Compliance.col(0) = Vecd(1 / E_[0], -poisson_[0] / E_[0], -poisson_[1] / E_[0]);
    Compliance.col(1) = Vecd(-poisson_[0] / E_[0], 1 / E_[1], -poisson_[2] / E_[1]);
    Compliance.col(2) = Vecd(-poisson_[1] / E_[0], -poisson_[2] / E_[1], 1 / E_[2]);

?

The definition of mu also has problems. It should be:

Mu_[0] = G_[0] + G_[2] - G_[1];
Mu_[1] = G_[1] + G_[0] - G_[2];
Mu_[2] = G_[2] + G_[1] - G_[0];

The sound speed cannot be defined by E_max and nu_max, as the material parameter relation derived from isotropic material no longer holds for the orthotropic case. I think we can replace it by lambda_max + 2/3*G_max.

The result of the test case is still weird after making those corrections. I'll also check the implementation of PK2 stress
@WeiyiVirtonomy WeiyiVirtonomy changed the title Lambda calculation of OrthotropicSolid seems to be wrong OrthotropicSolid seems to be wrong Nov 19, 2024
@WeiyiVirtonomy
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@DongWuTUM Could you take a look at this issue? This material class is problematic

@DongWuTUM
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I am not sure. Could you share some references?

@WeiyiVirtonomy
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I am not sure. Could you share some references?

You might take the implementation of FEbio as a reference (or anything else about the linear orthotropic material):
code, tutorial

@WeiyiVirtonomy WeiyiVirtonomy mentioned this issue Nov 20, 2024
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@Xiangyu-Hu
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@DongWuTUM Could you take a look at this issue? This material class is problematic

This model is added by Virtonomy.

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@Xiangyu-Hu @DongWuTUM @WeiyiVirtonomy