Damper


Symbol:
Identifier: Mechanics.Translation.Damper
Version: 3.6
File: Mechanics.cat
Connectors: Mechanical Connector (linear) ctr1 connectable to elements of the Linear Mechanics library
Mechanical Connector (linear) ctr2 connectable to elements of the Linear Mechanics library
Parameters: Damping b not visible, if rigid==true
Rigid rigid if true, the element behaves as rigid
Initial Preload of Damper kindPD
  • "No Preload or Preload from Environment"
  • "Preload Velocity Difference"
  • "Preload Force"
Initial Velocity Difference dv0 only visible if kindPD=="Preload Velocity Difference"
Initial Damping Force Fd0 only visible if kindPD=="Preload Force"
Results: Internal Force Fi
Displacement Diff. dx
Velocity Difference dv
Power Loss Pl not visible, if rigid==true
External Power Pe only visible, if rigid==true
  • Lineare oder nicht-lineare Dämpfung zwischen zwei Körpern (Massen) oder gegen Umgebung
  • Optional Berücksichtigung einer initialen Vorspannung
  • Linear or non-linear damping between two bodies (masses) or against environment
  • Option: Consideration of an initial preload

Description:

This Damper model represents a linear (translational) damper. Thus it allows to realize absolute as well as relative viscous (i.e., speed-proportional) dampings.

Parameters:

General Parameters

  • The damper is parameterized by the damping ("constant") b.
  • If rigid is true, the element behaves as rigid, which means, it behaves as a Constraint with dx==0. In this case, the damping b is deactivated.

Initial Values

This group contains the enumeration kindPD and (depending on the setting of kindPD) dv0 and Fd0 for the preload of the damper.

  • The enumeration kindPD holds a selection of initial states of the damper:
    • "No Preload or Preload from Environment": This is the default selection. The damper is initially unloaded or will be pre-loaded by the environmental conditions (i.e. initial values at the connections at ctr1 or ctr2).
    • "Preload Velocity Difference": The damper is pre-loaded. This option activates the parameter dv0, the initial velocity difference.
    • "Preload Force": The damper is pre-loaded. This option activates the parameter Fd0, the pre-load force.
  • dv0 ... initial velocity difference of the damper
    • The value of this parameter must be consistent with the initial values of the connections at ctr1 (-> v10) and ctr2 (-> v20):
      dv0 == v10 - v20
      To fulfill this constraint, it is recommend to unfixv10 or v20 (-> the corresponding initial values of the connections).
  • Fd0 ... the initial damping force or pre-load
    • Here, dv0 will be computed internally by dv0 = Fd0/b taking the damping b into account.
    • Note: Also here the initial values of the velocities must be consistent (see above).
If a pre-loaded spring is specified (setup of dv0 or Fd0) an initial constraint will be taken into account. Therefore, the initial values of the connected elements at ctr1 and ctr2 must be consistent with this initial constraint (dv0 == v10 - v20).
Only one of the initial velocities of the environmental structures at ctr1 or ctr2 must be fixed (see also Constraint model).

Results:

  • The Internal Force of the damper results from the damping b and the speed difference as
  • The Displacement Difference is the difference between the current displacements of the connections, which are linked to the connectors ctr1 and ctr2:
    = ctr1.x - ctr2.x
  • The Velocity Difference results from the velocities at the connectors respectively:
    = ctr1.v - ctr2.v
  • The Power Loss is computed as:
  • If rigid == true, the external power Pe is computed:

    If this power is positive, the element acts as a power source, otherwise it consumes power.

Remarks:

For modeling relative dampings the element is placed between two linear components. For an absolute damping one of the connectors is connected to a fixation (using the element type Preset), or remains unconnected (this is equivalent to a fixation).