Command manual

Command list

LOAD_DAMPING

Loads
*LOAD_DAMPING
"Optional title"
entype, enid, cid, $\mu$, $c_{dec}$

Parameter definition

VariableDescription
entype Entity type
options: N, NS, P, PS, ALL
enid Entity ID
cid ID of a CURVE or FUNCTION defining the mass damping coefficient $C$ versus time
$\mu$ Viscous damping coefficient
$c_{dec}$ Viscous decay coefficient

Description

This command is used to define mass damping and viscous damping for a given subset of the model. The mass damping force $\mathbf{F}_i$ acting a node $i$ is defined as:

$\mathbf{F}_i = -C \cdot m_i \cdot \mathbf{v}_i$

where $C$ is the damping coefficient defined by the CURVE or FUNCTION with ID cid, $m_i$ is the node mass and $\mathbf{v}_i$ is the node velocity. The viscous damping is defined as an artificial material viscosity. This viscosity produces an extra, strain rate dependent, stress term $\mathbf{\sigma}_\mu$:

$\displaystyle{ \mathbf{\sigma}_\mu = \frac{\mu}{c_{dec}} \int_0^t \dot{\mathbf{\epsilon}}(\tau) \cdot \mathrm{e}^{(\tau-t)/c_{dec}} \mathrm{d}\tau }$

Example

Viscous damping

A complete model of two tip loaded cantilever beams, one with applied viscous damping and one without.

*PARAMETER
#
# viscous damping coefficients
mu = 1.0e7
cdec = 1.0e-5
#
# tip load
F = 2*1000
*TIME
0.01
*COMPONENT_BOX
"undamped cantilever"
1, 1, 10, 1, 1
0, 0, 0, 0.1, 0.01, 0.01
*COMPONENT_BOX
"damped cantilever"
2, 2, 10, 1, 1
0, 0.05, 0, 0.1, 0.06, 0.01
*CHANGE_P-ORDER
ALL, 0, 2
*MAT_ELASTIC
1, 7800.0, 210.0e9, 0.3
*PART
"undamped cantilever"
1, 1
"damped cantilever"
2, 1
#
# damping
*LOAD_DAMPING
P, 2, 0, [%mu], [%cdec]
#
# constrain base
*BC_MOTION
G, 1, XYZ
*GEOMETRY_BOX
1
-0.001, 0, 0, 0.001, 0, 0
#
# constant tip load
*LOAD_FORCE
G, 2, Z, 1
*FUNCTION
1
-%F
*GEOMETRY_BOX
2
0.099, 0, 0, 0.101, 0, 0
*END
Viscous damping applied to a cantilever beam
Viscous damping applied to a cantilever beam