The Structural Dynamics Modifications (SDM) method calculates the effects of making physical modifications to a structure on its modes of vibration.
With SDM, physical elements can be added to (or subtracted from) a structure model, and its new modes are calculated.
All structural modifications are converted to changes in the mass, stiffness & damping properties of the structure
The mass, stiffness & damping changes are then used together with the modes of the unmodified structure to calculate the modes of the modified structure
To use the SDM commands, only the modes of the unmodified structure together with the FEA modification elements attached to a structure model are required
The modes of the unmodified structure must be a set of mode shapes scaled to Unit Modal Masses (a modal model).
Structural Dynamics Modification (SDM) Calculation Diagram