Mechanical resonance

Mechanical resonance is the large-amplitude vibration of a mechanical system when periodic forcing approaches one of its natural frequencies. Its strength depends on damping and how closely the forcing matches a natural frequency.

Natural frequency: A frequency at which a system oscillates freely after being displaced from equilibrium. Resonance occurs when forcing approaches one of the system’s free-oscillation frequencies.
Tacoma Narrows Bridge collapse: The 1940 collapse of a suspension bridge near Tacoma, Washington, after wind-driven oscillations grew dramatically. The collapse illustrates dangerous structural oscillation, though its principal mechanism was aeroelastic flutter rather than simple resonance.
Simple harmonic motion: Periodic motion in which the restoring force is proportional to displacement and directed toward equilibrium. It is the idealized free motion underlying the basic resonant oscillator.
Aeroelastic flutter: A self-excited oscillation caused by interaction between aerodynamic forces and a structure’s motion. Unlike ordinary forced resonance, flutter can draw energy continuously from airflow and need not match a fixed forcing frequency.
Damping: The reduction of oscillation amplitude as a system dissipates mechanical energy. Damping limits resonant amplitude and determines how sharply response peaks near a natural frequency.
Vibration isolation: The reduction of vibration transmitted from a source to a protected structure or device. Isolation systems must avoid or control resonant frequencies that can amplify transmitted motion.
Mass-spring-damper system: A mechanical model consisting of a mass, an elastic spring, and a dissipative damper. This standard model captures natural frequency, forced response, and damping in one system.
Parametric resonance: Oscillation growth caused by periodic variation of a system parameter, such as stiffness or length. It can amplify motion through parameter modulation rather than a periodic external force near a natural frequency.
Forced oscillation: Oscillation sustained by an external time-varying force. Mechanical resonance is the amplified response of a forced oscillator near a natural frequency.
Tuned mass damper: A device that uses a secondary mass and damping to reduce vibration in a structure near a target frequency. It counteracts resonant motion by shifting energy into a deliberately tuned auxiliary oscillator.

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