/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 β grnd_ID skew_ID Tstart Tstop

Format 2 (full format)

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/DAMP/INTER/damp_ID
damp_title
Nb_time_step
α β xx grnd_ID Skew_ID Tstart Tstop
αyy β yy        
αzz β zz        

Definitions

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)

[ 1 s ]
β Stiffness damping coefficient

β is used for all DOF.

(Real)

[ s ]
grnd_ID Node group identifier

(Integer)

 
Skew_ID Skew identifier

(Integer)

 
Tstart Start time

(Real)

[ s ]
Tstop Stop time

Default = 1030 (Real)

[ s ]
αxx Mass damping coefficient for rotational DOF (in xx direction) 6

(Real)

[ 1 s ]
αyy Mass damping coefficient for rotational DOF (in yy direction) 6

(Real)

[ 1 s ]
αzz Mass damping coefficient for rotational DOF (in zz direction) 6

(Real)

[ 1 s ]
β xx Stiffness damping coefficient for rotational DOF (in xx direction) 6

(Real)

[ s ]
β yy Stiffness damping coefficient for rotational DOF (in yy direction) 6

(Real)

[ s ]
β zz Stiffness damping coefficient for rotational DOF (in zz direction) 6

(Real)

[ s ]

Comments

  1. The damping parameters can be modified with the Engine option /DAMP.
  2. Rayleigh damping is applied only on rotational DOF and is computed as:(1)
    C=αI+βK
    (2)
    C i =α m i +β k ri
    (3)
    C c r i t = 4 m i k i
    Where,
    C
    Viscosity matrix
    I
    Intertia matrix
    K
    Rotational stiffness matrix
    α and β
    Coefficients
    C i
    Nodal viscosity
    i ni
    Nodal inertia
    k ri
    Rotational nodal stiffness
    C c r i t
    Critical damping
  3. 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.
  4. The damping is active for nodes that are no longer in contact during Nb_time_step cycles.
  5. The same node cannot be referred by more than one /DAMP/INTER card.
  6. The coefficients in Format 2 are used to define non-isotropic damping in global reference system or in a local one if skew_ID is specified.
  7. /DAMP/INTER is only compatible with contacts TYPE7, TYPE10 and TYPE11.