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!DASHPOT_A

Definition of an axial dashpot.

For the two nodes connected by a 2-node connector element (element type 511), this defines a dashpot acting along the axis connecting those two nodes. Because a dashpot contributes only to the damping matrix, it is used in implicit dynamic analysis (!SOLUTION, TYPE=DYNAMIC with idx_eqa=1 in !DYNAMIC). It has no effect in static analysis. To define a dashpot connecting specific degrees of freedom, use !DASHPOT_D.

Definition in the Mesh Data

!DASHPOT_A specifies the damping coefficient as a material property; this keyword alone does not create a dashpot. The following two definitions are required in the mesh data (msh).

• An element of type 511 whose connectivity consists of the two nodes connected by the dashpot (→ !ELEMENT)
• A section with TYPE=INTERFACE for that element group (→ !SECTION). For MATERIAL, specify the name of the material whose damping coefficient is defined by this keyword

When solid elements and connector elements are mixed, use separate element groups and define !SECTION for each.

Parameters

None

** 2nd line **

Specify the axial dashpot coefficient.

    (2nd line) DAMPING_COEFF

Variable name	Attribute	Description
DAMPING_COEFF	R	Damping coefficient

Example

When defining an axial dashpot (damping coefficient 100) connecting node 1 and node 5, mixed with solid elements (element group ESLD)

msh

!ELEMENT, TYPE=511, EGRP=EDAMP
3, 1, 5
!SECTION, TYPE=SOLID,     EGRP=ESLD,  MATERIAL=MATERIAL1
1.0
!SECTION, TYPE=INTERFACE, EGRP=EDAMP, MATERIAL=MATERIAL2
1.0

cnt

!SOLUTION, TYPE=DYNAMIC, NONLINEAR
!MATERIAL, NAME=MATERIAL2
!DASHPOT_A
100

Notes

• A dashpot contributes only to the damping matrix. In static analysis (!SOLUTION, TYPE=STATIC), it does not contribute to the stiffness matrix and therefore has no effect.
• A material for which a damping coefficient is defined is treated as a material dedicated to connector elements. It cannot be shared with solid elements by assigning elastic properties to the same material name, so use a different material name from that of the solid elements.
• An axial dashpot has damping only in the axial component. As with a spring, directions normal to the axis must be supported by other elements or boundary conditions.

Related Items

• !DASHPOT_D
• !SPRING_A
• !DYNAMIC
• !ELEMENT
• !SECTION