/DAMP

Engine Keyword Used to modify the Rayleigh mass and stiffness damping coefficients defined using the Starter /DAMP option.

Format 1 (Short Format)

/DAMP/damp_ID

α $\beta$

/DAMP/damp_ID

Definitions

Field Contents SI Unit Example
damp_ID Identifier of damping option in Radioss Starter (/DAMP).
α Mass damping coefficient used for all DOF. $\left[\frac{\text{1}}{\text{s}}\right]$
$\beta$ Stiffness damping coefficient used for all DOF. $\left[\text{s}\right]$
${\alpha }_{x}$ Mass damping coefficient for translational degree of freedom (DOF) in x direction. $\left[\frac{\text{1}}{\text{s}}\right]$
${\alpha }_{y}$ Mass damping coefficient for translational DOF in y direction. $\left[\frac{\text{1}}{\text{s}}\right]$
${\alpha }_{z}$ Mass damping coefficient for translational DOF in z direction. $\left[\frac{\text{1}}{\text{s}}\right]$
${\alpha }_{xx}$ Mass damping coefficient for rotational DOF in xx direction. $\left[\frac{\text{1}}{\text{s}}\right]$
${\alpha }_{yy}$ Mass damping coefficient for rotational DOF in yy direction. $\left[\frac{\text{1}}{\text{s}}\right]$
${\alpha }_{zz}$ Mass damping coefficient for rotational DOF in zz direction. $\left[\frac{\text{1}}{\text{s}}\right]$
${\beta }_{x}$ Stiffness damping coefficient for translational DOF in x direction. $\left[\text{s}\right]$
${\beta }_{y}$ Stiffness damping coefficient for translational DOF in y direction. $\left[\text{s}\right]$
${\beta }_{z}$ Stiffness damping coefficient for translational DOF in z direction. $\left[\text{s}\right]$
${\beta }_{xx}$ Stiffness damping coefficient for rotational DOF in xx direction. $\left[\text{s}\right]$
${\beta }_{yy}$ Stiffness damping coefficient for rotational DOF in yy direction. $\left[\text{s}\right]$
${\beta }_{zz}$ Stiffness damping coefficient for rotational DOF in zz direction. $\left[\text{s}\right]$

1. Rayleigh α damping computation:(1)
$C=\alpha M+\beta K$
(2)
${C}_{i}=\alpha {m}_{i}+\beta {k}_{i}$
(3)
${\text{C}}_{\text{crit}}=\sqrt{4{\text{m}}_{\text{i}}{\text{k}}_{\text{i}}}$
(4)
$\frac{{\text{C}}_{\text{i}}}{{\text{C}}_{\text{crit}}}=\frac{\alpha }{2{\omega }_{\text{i}}}+\frac{{\beta \omega }_{\text{i}}}{2}$
Where,
$C$
Damping matrix
$M$
Mass matrix
$K$
Stiffness matrix
α and $\beta$
Coefficients
${C}_{i}$
Nodal damping matrix
${m}_{i}$
Nodal mass matrix
${k}_{i}$
Nodal stiffness matrix
${C}_{crit}$
Critical damping
2. This option can be used only if damping card (/DAMP) is defined in the Runname_0000.rad file.
3. Arbitrary coefficients alpha and beta may be declared in the Runname_0000.rad file and modified when repeating the option in the Radioss Engine file Runname_run#.rad.