This option is used to define viscous damping between two interacting surfaces. It must be used in conjunction with the *SURFACE INTERACTION, the *GAP, or the *INTERFACE option. In ABAQUS/Standard this option is primarily used to damp relative motions of the surfaces during approach or separation. In ABAQUS/Explicit this option is used to damp oscillations when using penalty or softened contact.
Products: ABAQUS/Standard ABAQUS/Explicit
Type: Model data in ABAQUS/Standard; History data in ABAQUS/Explicit
Level: Part Part Instance Assembly Model in ABAQUS/Standard; Step in ABAQUS/Explicit
Use this parameter to choose the dimensionality of the damping coefficient that is specified on the data line. The only option that is available in an ABAQUS/Standard analysis is DEFINITION=DAMPING COEFFICIENT.
Set DEFINITION=CRITICAL DAMPING FRACTION to use a unitless damping coefficient, 
. The damping forces are calculated with 
, where 
is the nodal mass, 
is the nodal contact stiffness (in units of 
), and 
is the rate of relative elastic slip between the surfaces. A default value of =0.03 is used for kinematic contact with softened behavior and penalty contact.
Set DEFINITION=DAMPING COEFFICIENT to specify damping in terms of a damping coefficient, 
, with units of pressure per relative velocity such that the damping forces will be calculated with 
, where 
is the nodal area and is the rate of relative elastic slip between the surfaces. If a contact area is not defined, such as may occur for node-based surfaces or for GAP- or ITT-type contact elements, coefficient units are force per relative velocity. For contact with three-dimensional beams or trusses, coefficient units are force per unit length per unit velocity.
Set this parameter equal to the tangential damping coefficient divided by the normal damping coefficient. This parameter affects only the tangential damping; the normal direction damping coefficient is defined on the data line below. Set this parameter equal to zero if no tangential damping is desired. The default is 0.0 in ABAQUS/Standard and 1.0 in ABAQUS/Explicit.
First (and only) line:
Damping coefficient.
The remaining data items are used only in ABAQUS/Standard analyses. For ABAQUS/Explicit damping is applied only when the surfaces are in contact, whereas for ABAQUS/Standard damping is applied independent of the open/close state.
Clearance at which the damping coefficient is zero, 
.
Fraction of the clearance interval between zero clearance and 
over which the damping coefficient is constant, 
. The default is 
.