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# NonlinearGurson1D

Uniaxial Nonlinear General Gurson Porous Model

## Theory

The yield function, hardening rule, flow rule are identical to that of the 3D version. Please check the [`NonlinearGurson`](/suanpan-manual/material/material3d/vonmises/nonlineargurson.md) model for details.

See also the corresponding section in [Constitutive Modelling Cookbook](https://github.com/TLCFEM/constitutive-modelling-cookbook/releases/download/latest/COOKBOOK.pdf).

The uniaxial version assumes the stress tensor possesses the following voigt form.

$$
\sigma=\begin{bmatrix}\sigma\_1&0&0&0&0&0\end{bmatrix},
$$

meaning that the elastic strain $$\varepsilon^e$$ is always

$$
\varepsilon^e=\varepsilon\_1^e\begin{bmatrix}1&-\nu&-\nu&0&0&0\end{bmatrix},
$$

where $$\nu$$ is Poisson's ratio.

## Recording

This model supports the following additional history variables to be recorded.

| variable label | physical meaning |
| -------------- | ---------------- |
| VF             | volume fraction  |


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