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 


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 


Description:
This Damper model represents a linear (translational) damper. Thus it allows to realize absolute as well as relative viscous (i.e., speedproportional) 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 preloaded by the environmental conditions (i.e. initial values at the connections at ctr1 or ctr2).
 "Preload Velocity Difference": The damper is preloaded. This option activates the parameter dv0, the initial velocity difference.
 "Preload Force": The damper is preloaded. This option activates the parameter Fd0, the preload 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 preload
 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).
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).