Validating a Modal Model

There are several ways to validate the Modal Model before using it with SDM commands to model the dynamics of the unmodified structure.

1. Synthesize FRFs using the UMM mode shapes and overlay the synthesized and experimental FRFs

2. Perform a ”round trip” SDM calculation

3. Calculate the Participation of the modes in an FEA modal model in each mode of an EMA or OMA modal model

 If EMA or OMA mode shapes are properly scaled, the Participation of each FEA shape in each EMA or OMA shape will be "1".

Round Trip SDM Calculation

1. Add a point Mass to the structure model, and its mass to the FEA Mass Properties list

2. Execute SDM | Calculate New Modes, and choose the modal model with the shapes of the unmodified structure

3. Save the new modes calculated by SDM in a Shape Table named "new mode shapes"

4. In the FEA Properties list, change the Mass value to "minus" the previous value already added

5. Execute SDM | Calculate New Modes again, and choose the "new mode shapes" Shape Table as the shapes of the unmodified structure..

6. Execute Display | MAC and compare the original mode shapes with the mode shapes obtained from the previous step