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hugary1995 committed Nov 19, 2024
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The Johnson-Cook plasticity model has the following form
\begin{equation}
\sigma = \sigma_0\left(A+B\left(\frac{\ep}{\ep0}\right)^n\right)\left(1+C\text{ln}\left(\frac{\epdot}{\epdot0}\right)\right)\left(1-\left(\frac{T-T_0}{T_m-T_0}\right)^m\right)
\sigma = \sigma_0\left(A+B\left(\frac{\ep}{\varepsilon_0^p}\right)^n\right)\left(1+C\text{ln}\left(\frac{\epdot}{\dot\varepsilon_0^p}\right)\right)\left(1-\left(\frac{T-T_0}{T_m-T_0}\right)^m\right)
\end{equation}

Where $\sigma_0$ is the unperturbed yield stress, $\ep0$ is the reference plastic strain, $\epdot0$ is the reference plastic strain rate, $T_m$ is the melting temperature, and $T_0$ is the reference temperature.
Where $\sigma_0$ is the unperturbed yield stress, $\varepsilon_0^p$ is the reference plastic strain, $\dot\varepsilon_0^p$ is the reference plastic strain rate, $T_m$ is the melting temperature, and $T_0$ is the reference temperature.
$A$,$B$,and $C$ are parameters of the Johnson-Cook model.

When put into a variational framework, the Johnson-Cook model defines the following plastic energy
\begin{equation}
\psi_p = \left[\left(1-Q\right)g_p \sigma_0 \ep \left(A\ep + B\ep0\left(\frac{\ep}{\ep0}\right)^{n+1}\frac{1}{n+1}\right)\right]f(T),\\
\psi_p^* = \left[Q \sigma_0\left(A+B\ep0\left(\frac{\ep}{\ep0}\right)^n\right)+\left(A+B\frac{\ep}{\ep0}\right)\left(C\text{ln}\left(\frac{\epdot}{\epdot0}\right)-C\right)\right]f(T),\\
f(T) = \left(\frac{T-T_0}{T_m-T_00}\right)
\psi_p = \left[\left(1-Q\right)g_p \sigma_0 \ep \left(A\ep + B\varepsilon_0^p\left(\frac{\ep}{\varepsilon_0^p}\right)^{n+1}\frac{1}{n+1}\right)\right]f(T),\\
\psi_p^* = \left[Q \sigma_0\left(A+B\varepsilon_0^p\left(\frac{\ep}{\varepsilon_0^p}\right)^n\right)+\left(A+B{\left(\frac{\ep}{\varepsilon_0^p}\right)^n}\right)\left(C\text{ln}\left(\frac{\epdot}{\dot\varepsilon_0^p}\right)-C\right)\right]f(T),\\
f(T) = \left(\frac{T-T_0}{T_m-T_0}\right)
\end{equation}

Additionally, the energy is split into energetic and dissipative portions using the Taylor-Quinney factor, $Q$.\\
The flow stresses are defined as the following

\begin{equation}
Y^{\text{eq}}=\left[\left(1-Q\right)\sigma_0\left(A+B\frac{\ep}{\ep0}\right)^n\right]f(T),\\
Y^{\text{vis}}=\left[Q\sigma_0\left(A+B\left(\frac{\ep}{\ep0}\right)^n\right)+\left(A+B\frac{\ep}{\ep0}\right)\left(C\text{ln}\left(\frac{\epdot}{\epdot0}\right)\right)\right]f(T)
Y^{\text{eq}}=\left[\left(1-Q\right)\sigma_0\left(A+B\frac{\ep}{\varepsilon_0^p}\right)^n\right]f(T),\\
Y^{\text{vis}}=\left[Q\sigma_0\left(A+B\left(\frac{\ep}{\varepsilon_0^p}\right)^n\right)+\left(A+B\frac{\ep}{\varepsilon_0^p}\right)\left(C\text{ln}\left(\frac{\epdot}{\dot\varepsilon_0^p}\right)\right)\right]f(T)
\end{equation}


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1 change: 1 addition & 0 deletions doc/content/theory/constitutive_models.md
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Expand Up @@ -33,6 +33,7 @@ We support both small deformation and large deformation. Several hyperelastic mo

- [Power-law hardening](PowerLawHardening.md)
- [Arrhenius-law hardening](ArrheniusLawHardening.md)
- [Johnson-Cook Hardening](JohnsonCookHardening.md)

## Phase-field fracture models

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