SDM | Add Tuned Absorbers

Models the addition of one or more tuned vibration absorbers to a structure.

A tuned absorber is modeled using a mass, spring, and damper.  The SDM method and sub-structuring is used to attach the tuned absorber mass to a structure using the spring and damper.

SDM calculates the new modes which result from attaching a tuned absorber mass to the structure with a spring and damper .

The new modes reflect the influence of the Tuned Absorber on the modes of the structure.

A Tuned Absorber s defined by the following parameters,

Absorber Spring

The Tuned Absorber FEA mass is attached to a Point & direction of a structure model using an FEA spring.  The stiffness of the spring is calculated using the formula,

FEA spring stiffness = Absorber FEA mass x (Absorber Frequency)2

Before Adding The Absorber

The using SDM to calculate the new modes, the following items are required,

  1. A Shape Table containing UMM mode shapes of the unmodified structure.

  2. A structure model containing the Point & direction where the Tuned Absorber will be attached.

  3. Mass, Force & Length units (chosen on the Units tab in the File | Structure Options box), that match the Force & Length units of the UMM mode shapes.

The UMM mode shapes must animate correctly on the structure model before using them with this command.

When this command is executed, the following dialog box will open;

Tuned Absorber Dialog Box.

For each Absorber,

Calculate New Modes

When the SDM calculation is completed, all Tuned Absorbers defined in the dialog box will have been added as new Point Masses to the structure model.