Erik Kostson
Ansys Employee
No worries.
The term how it performs is very wage - you say multiple failures, but the most important thing that we can model is typically fatigue failure - for that use the fatigue tool.

The part will just vibrate at the excitation frequency during 15 minutes, so that is all that will happen, and this is just a steady state vibration, which we then model with a harmonic response.

So there is no need to run a transient analysis for 15 minutes :), that does not need to be run.

With the fatigue tool under the excitation you have and at a certain driving frequency it will tell you what the life is (it does not have to be 15 min, it can be 1 sec if the loads are high).

If we run for 15 minutes transient you will just see a steady state oscillation at the driving frequency - which is the same as the harmonic response at that frequency, but of course we do not need to run something for 15 minutes which can take a very long time. That is why harmonic is so good for these type of vibration tests.

See the course for more info please and the help manual structural analysis guide:
4.1. Uses for Harmonic Analysis
5 , Transient analysis

All the best