Material properties
Attention: This command is in the beta stage and the format may change over time.
"Optional title"
mid, $\rho$, $E$, $\nu$, did
$C_v$, $\gamma$, $e_0$, $v$, fid, $T_i$, $p_i$
local, $A$, $B$, $n$
Parameter definition
mid Unique material identification number
$\rho$ Density
$E$ Young's modulus (optional)
default: not used
$\nu$ Posson's ratio (only used if $E \gt 0$)
did Damage property command ID
$C_v$ Heat capacity
$\gamma$ Heat capacity ratio $(C_p/C_v)$
$e_0$ Combustion energy per unit mass
$v$ Initial co-volume (dimensionless)
fid Burn rate function ID
$T_i$ Ignition temperature
$p_i$ Ignition pressure
local Local burn rate flag
$A$ Initial yield strength
$B$ Hardening parameter
$n$ Hardening exponent

This material command is used to model unburned propellant as rigid or elasto-plastic grains and its combustion products as discrete particles. The grains are assumed rigid, unless $E \gt 0$.

If $E \gt 0$ then the flow stress is defined as:

$\displaystyle{ \sigma_y = A + B(\varepsilon_{eff}^p)^n }$

By default (local=0) the burn rate is uniform for each grain. That is, the average pressure and temperature is calculated and used for all element faces on the grain. If local=1, then the local pressure and temperature defines the local burn rate for each individual element face.

The command needs to be combined with POWDER_BURN_IGNITE and PARTICLE_DOMAIN. POWDER_BURN_IGNITE is used to describe the ignition location and PARTICLE_DOMAIN defines gas-structure contacts and limits the region in space where the combustion products (discrete particles) are modeled. The number of discrete particles that are used to model the combustion products are specified in the PART command (parameter $N_{perode}$).

Internal ballistics (burning propellant)

Propellant grains burning in a simple internal ballistics demonstration model.

rho = 2200.0, "powder density"
Cv = 700.0, "heat capacity"
gamma = 1.4, "Cp/Cv ratio"
e0 = 1.2e6, "combustion energy per unit mass"
cvol = 0.3, "initial co-volume"
a = 1.0e-5, "burn rate parameter 1"
n = 0.6, "burn rate parameter 2"
c = 0.0001, "burn rate parameter 3"
patm = 1.0e5, "burn rate parameter 4"
Ti = 500.0, "ignition temperature"
pi = 1.0e6, "ignition pressure"
xi = 0.0, "ignition point X"
yi = 0.0, "ignition point Y"
zi = 0.0, "ignition point Z"
ti = 0.0, "ignition time"
Ri = 0.02, "ignition radius"
Np = 800000, "total number of particles"
# --- Propellant material properties ---
2, [%rho]
[%Cv], [%gamma], [%e0], [%cvol], 123, [%Ti], [%pi]
"burn rate"
%a*max(%patm,p)^%n + %c
# --- Ignition location ---
"ignition location"
[%xi], [%yi], [%zi], [%ti], [%Ri]
# --- Define number of particles in PART command ---
2, 2, 0, 0, 0, 3.0e-8, 0, 0, [%Np]
# --- Define region in space where the discrete particles are active ---
ALL, 0, 0
-0.06, -0.06, -0.01, 0.06, 0.06, 1.0