Erik Kostson
Ansys Employee

That is correct - harmonic analysis is in the frequency domain (not in time domain like a transient).

Time can come in as you said if one uses the fatigue tool in a harmonic analysis - that will give how many seconds the component can run at the excitation frequency before it fails.

This discussion might be useful if you look at the fatigue tool inside a harmonic response.

Finally one would not run transient for 15 minutes - since the system is in a steady state vibration harmonic is the analysis one could use.

We have courses on the subject which are useful:

All the best