/DAMP/INTER

Block Format Keyword

/DAMP/INTER - Rayleigh damping of nodes with non-zero contact force

Description

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
				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
				grnd_ID	skew_ID	Tstart		Tstop

Field	Contents	SI Unit Example
damp_ID	Damping identifier (Integer, maximum 10 digits)
damp_title	Damping title (Character, maximum 100 characters)
Nb_time_step	Optional number of time steps (Comment 4) Default = 20 (Integer)
	Mass damping coefficient is used for all DOF. (Real)
	Stiffness damping coefficient is used for all DOF. (Real)
grnd_ID	Node group identifier (Integer)
skew_ID	Skew identifier (Integer)
Tstart	Start time (Real)
Tstop	Stop time Default = 1030 (Real)
	Mass damping coefficient for rotational DOF (in xx direction) (Comment 6) (Real)
	Mass damping coefficient for rotational DOF (in yy direction) (Comment 6) (Real)
	Mass damping coefficient for rotational DOF (in zz direction) (Comment 6) (Real)
	Stiffness damping coefficient for rotational DOF (in xx direction) (Comment 6) (Real)
	Stiffness damping coefficient for rotational DOF (in yy direction) (Comment 6) (Real)
	Stiffness damping coefficient for rotational DOF (in zz direction) (Comment 6) (Real)

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 follows:

[C] = [I] + [K]

Where,

[C] is the viscosity matrix

[I] is the inertia matrix

[K] is the rotational stiffness matrix

and are coefficients

Ci is the nodal viscosity

ini is the nodal inertia

kri is the nodal rotational stiffness

Ccrit is the 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/INTR is only compatible with contacts TYPE7, TYPE10 and TYPE11.