# XDAMP

Bulk Data Entry Defines the values for Raleigh damping for geometric nonlinear dynamic analysis.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
XDAMP DID GSID ALFA BETA

## Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
XDAMP 100 34 3.0 1.0

## Definitions

Field Contents SI Unit Example
DID Unique damping identification number.

(Integer ˃ 0)

GSID Grid set identification number. Damping is applied to the grid points in this set.

Default = all grids in the model (blank or Integer ˃ 0)

ALFA Factor for the stiffness matrix contribution.

(Real ˃ 0)

BETA Factor for the mass matrix contribution.

(Real ˃ 0)

## Comments

1. Rayleigh damping is applied to all geometric nonlinear dynamic analysis subcases, implicit and explicit. It is ignored in all other subcases.
2. In implicit dynamic analysis damping is applied to all grid points and GSID is ignored. Multiple XDAMP is not allowed in implicit dynamic analysis.
3. XDAMP and PARAM W3/G are mutually exclusive.
4. Grid sets in all XDAMP statements must contain unique sets of grid points.
5. The viscous damping matrix B is calculated from the mass matrix M and stiffness matrix K using:(1)
$B=ALFA\cdot M+BETA\cdot K$
6. This card is represented as an interface in HyperMesh.