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!DASHPOT_D

Definition of dashpot with specified degrees of freedom.

For the two nodes connected by a 2-node connector element (element type 511), a dashpot connecting the degree of freedom DOF1 of node 1 and the degree of freedom DOF2 of node 2 is defined. The direction of the dashpot is determined by the degree-of-freedom numbers and does not follow the deformation of the model. A dashpot contributes only to the damping matrix, so it is used in implicit dynamic analysis (!SOLUTION, TYPE=DYNAMIC with idx_eqa=1 of !DYNAMIC). It has no effect in static analysis. To define a dashpot acting along the axis connecting the two nodes, use !DASHPOT_A.

Node 1 and node 2 here are the first and the second node given as the connectivity of !ELEMENT.

Definition in the Mesh Data

!DASHPOT_D gives the damping coefficient as a material property; it does not create a dashpot by itself. The following two definitions are required in the mesh data (msh).

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

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

Parameter

None

** 2nd Line or later **

Define dashpot coefficient for specified degrees of freedom. Write one line for each pair of degrees of freedom; dashpots for several pairs can be defined by writing several lines.

    (2nd line) DOF1, DOF2, DAMPING_COEFF
Parameter Name Attributions Contents
DOF1 I Degree of freedom number for node 1 (1,2,3)
DOF2 I Degree of freedom number for node 2 (1,2,3)
DAMPING_COEFF R Damping coefficient

Example of Use

When defining a dashpot connecting node 1 and node 5, mixed with solid elements (element group ESLD), with a different damping coefficient in each of the x, y and z directions

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_D
1, 1, 100.0
2, 2, 300.0
3, 3, 400.0

Note:

  • A dashpot contributes only to the damping matrix. It does not contribute to the stiffness matrix and therefore has no effect in static analysis (!SOLUTION, TYPE=STATIC).
  • When different degree-of-freedom numbers are given to DOF1 and DOF2, the dashpot connects one direction of node 1 with another direction of node 2. To obtain a dashpot acting in the same direction, give the same number to DOF1 and DOF2.
  • A material with a damping coefficient is treated as a material dedicated to connector elements. It cannot be shared with solid elements by also giving elastic properties to it, so use a material name different from that of the solid elements.