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!SPRING_D

Definition of a spring with specified degrees of freedom.

For the two nodes connected by a 2-node connector element (element type 511), this defines a spring connecting degree of freedom DOF1 of node 1 to degree of freedom DOF2 of node 2. The spring direction is determined by the degree-of-freedom numbers and does not follow deformation of the model. To define a spring acting along the axis connecting the two nodes, use !SPRING_A.

Here, node 1 and node 2 are the first and second nodes, respectively, in the connectivity specified by !ELEMENT.

Definition in the Mesh Data

!SPRING_D specifies the spring constant as a material property; this keyword alone does not create a spring. 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 spring (→ !ELEMENT)
  • A section with TYPE=INTERFACE for that element group (→ !SECTION). For MATERIAL, specify the name of the material whose spring constant is defined by this keyword

Parameters

None

** Second and subsequent lines **

Specify the coefficient of the spring with specified degrees of freedom. Write one line for each pair of degrees of freedom; multiple pairs can be assigned springs by writing multiple lines.

    (2nd line) DOF1, DOF2, SPRING_COEFF
Variable Type Description
DOF1 I Degree-of-freedom number of node 1 (1,2,3)
DOF2 I Degree-of-freedom number of node 2 (1,2,3)
SPRING_COEFF R Spring constant

Example

When connecting node 1 and node 2 and assigning different spring constants in the x, y, and z directions

msh

!ELEMENT, TYPE=511, EGRP=ESPRING
1, 1, 2
!SECTION, TYPE=INTERFACE, EGRP=ESPRING, MATERIAL=SPRING1
1.0

cnt

!MATERIAL, NAME=SPRING1
!SPRING_D
1, 1, 100.0
2, 2, 300.0
3, 3, 400.0

Notes

  • If different degree-of-freedom numbers are specified for DOF1 and DOF2, the spring connects displacement in one direction at node 1 to displacement in a different direction at node 2. To define a spring in the same direction, specify the same number for DOF1 and DOF2.
  • No stiffness from this spring is added to degrees of freedom for which no spring is defined. Specify all required degree-of-freedom pairs, or constrain them with boundary conditions.
  • A material for which a spring constant 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.
  • !SPRING_D is a connector-element spring connecting two nodes and serves a different purpose from !SPRING, which is a boundary condition that elastically supports a node against the ground.

See Also