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This task will show you how to define the
damping set in a Dynamic Response Analysis case. |
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Only available with the Generative Dynamic
Response Analysis (GDY) product. |
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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. |
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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.
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Double-click the damping set from the specification tree.
In this particular case, double-click the
Damping.1 object.
The Damping Choice dialog box appears.
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- Name: if needed, you can change the name of the
damping set.
- Damping type:
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Select the desired Damping type.
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The modal damping is a fraction of the critical
damping.
The critical damping is computed as follow:
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where m is the mass of the system and
k the stiffness of the system. |
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The Rayleigh damping is defined as follow:
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where [M] is the mass matrix, [K]
is the stiffness matrix. |
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Compute the frequency solution.
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Click the Component edition button
to define the damping parameters.
The Damping Definition dialog box appears.
Modal Damping Definition
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- 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.
Multi-selection is available in this case.
Rayleigh Damping Definition
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- 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.
Multi-selection is available in this case.
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Define the desired damping parameters and click OK
in the Damping Choice dialog box.
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Click OK in the Damping Definition dialog box.
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