MAT_JH_CERAMIC
Material properties
"Optional title"
mid, $\rho$, $G$
$A$, $B$, $C$, $m$, $n$, $\dot\varepsilon_0$, $T$
$HEL$, $p_{\mathrm{HEL}}$, $\beta$, $D_1$, $D_2$, $K_1$, $K_2$, $K_3$
erode
Parameter definition
Description
The Johnson-Holmquist ceramic model (JH-2) is used to model brittle materials having a higher strength in compression than in tension. The yield criterion and flow rule follow J2 plasticity. A bulking pressure term is added to account for dilatation during deviatoric plastic flow. The figure below shows the von Mises plastic flow stress as function of pressure and damage.
Damage evolves according to:
$\dot D = \frac{\dot\varepsilon_{eff}^p}{\varepsilon_{fail}}$
where:
$\varepsilon_{fail} = D_1 \left( \frac{T + p}{p_{HEL}} \right)^{D_2}$
The elastic pressure-volume relationship is cubic in compression:
$p_{elastic} = K_1 \mu + K_2 \mu^2 + K_3 \mu^3 \;\;\; \mu > 0$
and linear in tension:
$p_{elastic} = K_1 \mu \;\;\; \mu \lt 0$
where:
$\mu = \rho/\rho_0 - 1$
It is assumed that a fraction $\beta$ of the elastic deviatoric strain energy that is being released as damage grows is transformed into pressure (the rest dissipates into heat). This is the so called bulking pressure. Assuming an incremental release of elastic deviatoric strain energy $\Delta U$, the incremental bulking pressure is defined as:
$\Delta p_{bulk} = \sqrt{ p^2 + 2 \beta K_1 \Delta U} - p$
Here $p$ is the total pressure:
$p = p_{elastic} + p_{bulk}$
