/DAMP/INTER
Block Format Keyword The card is intended to apply Rayleigh damping to the nodes inside of specified contact to increase its stability and reduce results scattering due to small variations of initial or boundary conditions.
Format 1 (short format)
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/DAMP/INTER/damp_ID  
damp_title  
Nb_time_step  
α  $\beta $  grnd_ID  skew_ID  T_{start}  T_{stop} 
Format 2 (full format)
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/DAMP/INTER/damp_ID  
damp_title  
Nb_time_step  
α  $\beta $ _{xx}  grnd_ID  Skew_ID  T_{start}  T_{stop}  
α_{yy}  $\beta $ _{yy}  
α_{zz}  $\beta $ _{zz} 
Definition
Field  Contents  SI Unit Example 

damp_ID  Damping
identifier. (Integer, maximum 10 digits) 

damp_title  Damping
title. (Character, maximum 100 characters) 

Nb_time_step  Number of time steps.
4
Default = 20 (Integer) 

α  Mass damping
coefficient. α is used for all DOF. (Real) 
$\left[\frac{\text{1}}{\text{s}}\right]$ 
$\beta $  Stiffness damping
coefficient. $\beta $ is used for all DOF. (Real) 
$\left[\text{s}\right]$ 
grnd_ID  Node group
identifier. (Integer) 

Skew_ID  Skew
identifier. (Integer) 

T_{start}  Start
time. (Real) 
$\left[\text{s}\right]$ 
T_{stop}  Stop time. Default = 10^{30} (Real) 
$\left[\text{s}\right]$ 
α_{xx}  Mass damping coefficient
for rotational DOF (in xx direction). 6 (Real) 
$\left[\frac{\text{1}}{\text{s}}\right]$ 
α_{yy}  Mass damping coefficient
for rotational DOF (in yy direction). 6 (Real) 
$\left[\frac{\text{1}}{\text{s}}\right]$ 
α_{zz}  Mass damping coefficient
for rotational DOF (in zz direction). 6 (Real) 
$\left[\frac{\text{1}}{\text{s}}\right]$ 
$\beta $ _{xx}  Stiffness damping
coefficient for rotational DOF (in xx direction).
6 (Real) 
$\left[\text{s}\right]$ 
$\beta $ _{yy}  Stiffness damping
coefficient for rotational DOF (in yy direction).
6 (Real) 
$\left[\text{s}\right]$ 
$\beta $ _{zz}  Stiffness damping
coefficient for rotational DOF (in zz direction).
6 (Real) 
$\left[\text{s}\right]$ 
Comments
 The damping parameters can be modified with the Engine option /DAMP.
 Rayleigh damping is applied only on
rotational DOF and is computed as:
(1) $$C=\alpha I+\beta K$$(2) $${C}_{i}=\alpha {m}_{i}+\beta {k}_{ri}$$(3) $${C}_{crit}=\sqrt{4{m}_{i}{k}_{i}}$$Where, C
 Viscosity matrix
 I
 Intertia matrix
 K
 Rotational stiffness matrix
 α and $\beta $
 Coefficients
 ${C}_{i}$
 Nodal viscosity
 ${i}_{ni}$
 Nodal inertia
 ${k}_{ri}$
 Rotational nodal stiffness
 ${C}_{crit}$
 Critical damping
 The damping is applied to all the nodes of the prescribed node group (grnd_ID) that are subjected to contact forces. The specification of grnd_ID is compulsory.
 The damping is active for nodes that are no longer in contact during Nb_time_step cycles.
 The same node cannot be referred by more than one /DAMP/INTER card.
 The coefficients in Format 2 are used to define nonisotropic damping in global reference system or in a local one if skew_ID is specified.
 /DAMP/INTER is only compatible with contacts TYPE7, TYPE10 and TYPE11.