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# Direct frequency response analysis

## Direct frequency response analysis

(OP)
Dear Users,

I have to do a response analysis of a certain construction (NX Siemens, Nastran solver 108, Direct frequency response analysis)

How do you define such excitation:
Excitation: 9.81 m/s² ≈1 g
Frequency Range: 10…..500 Hz
Sine-Sweep: 0.5 octave / min

Regards, Peter

### RE: Direct frequency response analysis

I don't know if it is your question, but there can be subleties involved when we try to give a math expression for a swept sin. In particular, see this thread: thread384-29248: Swept sine spectrum puzzler

The easy bottom line to that wandering thread - try plotting your proposed analytical expression (like op of linked thread did) to see if the apparent frequency matches what you intended or a factor of 2 different.

=====================================
(2B)+(2B)' ?

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