Harmonic Response Analysis — Frequency Domain FRF
Frequency response functions, modal superposition vs. direct methods, damping in frequency domain, and resonance identification.
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Quick Explainer
What does a frequency response function (FRF) tell me?
An FRF is the ratio of output (displacement, velocity, or acceleration) to input force as a function of frequency. Peaks reveal resonances. The peak height indicates damping level — a sharp tall peak means low damping and dangerous amplification at that frequency.
When should I use direct frequency response instead of modal superposition?
Modal superposition assumes proportional damping. If you have non-proportional damping (localized dampers), heavily damped modes, or need accuracy at high frequencies where many modes contribute, direct frequency response is more reliable — just much slower to compute.