
This task will show you how to define the
damping set in a Dynamic Response Analysis case. 

Only available with the Generative Dynamic
Response Analysis (GDY) product. 

Defining a damping set allows you to define the
resulting damping of the part once the force has been applied to this part.
You can choose between two damping types: Modal or Rayleigh.
By default, the damping is modal. 

Open the
sample57.CATAnalysis document from the samples directory.
In this particular example, a dynamic response case and a
modulation set have been already inserted.



Doubleclick the damping set from the specification tree.
In this particular case, doubleclick the
Damping.1 object.
The Damping Choice dialog box appears.
 Name: if needed, you can change the name of the
damping set.
 Damping type:


Select the desired Damping type.

The modal damping is a fraction of the critical
damping.
The critical damping is computed as follow:
where m is the mass of the system and
k the stiffness of the system. 

The Rayleigh damping is defined as follow:
where [M] is the mass matrix, [K]
is the stiffness matrix. 

Compute the frequency solution.

Click the Component edition button
to define the damping parameters.
The Damping Definition dialog box appears.
Modal Damping Definition

 Global ratio: lets you define the factor of the
critical damping for all the modes (in %).
 Definition mode by mode: lets you define the
critical damping ratio (in %) independently for each
mode.
Multiselection is available in this case.
Rayleigh Damping Definition

 Global ratio: lets you define the Alpha (mass
ratio) and/or Beta (stiffness ratio) coefficients
for all the modes.
 Alpha (mass ratio): lets you define the factor of
the mass ratio (in %).
 Beta (stiffness ratio): lets you define the factor
of the stiffness ratio (in %).
 Definition mode by mode: lets you define the
Alpha (mass ratio) and/or Beta (stiffness ratio)
coefficients (in %) independently for each selected
mode.
Multiselection is available in this case.


Define the desired damping parameters and click OK
in the Damping Choice dialog box.

Click OK in the Damping Definition dialog box.

