“Harmonic resonance is the bane of mechanical engineers, and especially aircraft engines.”
I’d add bridge/ structural engineers and provide an example of that bridge in the Pacific NW that shook itself to pieces back in the 1940s.
Galloping Gertie. Tacoma Narrows bridge.
Although recently there was report it wasn’t really natural frequency issue.
I used to experience harmonic resonance on a Dodge pickup. It would happen in the rear springs at about 50 mph. Leaf springs. I had to either speed up or slow down to get it to stop. Annoying.
Galloping Gertie was a special case of induced resonance. (I am an EE not an ME.) The light poles on the roadway caused turbulence in the airflow around them, aeoli. When the roadbed tipped they shed the aeoli, which induced an aerodynamic impulse exactly in phase with the resonant frequency of the bridge. The tipping of the roadbed caused the impulse, which reinforced the tipping of roadbed, like the escapement on a pendulum in a clock, only a clock pendulum stabilizes when the energy dissipated on each cycle equals the energy supplied by the escapement. For poor Gertie, mechanical failure preceded stabilization.
https://www.youtube.com/watch?v=j-zczJXSxnw