Resonance is a condition where a machine is operating at a frequency close to or at the natural frequency of its structure. This condition excites the structure and causes high amplitude vibrations; this will show up as a “hump” at the resonant frequency in the spectral data (Figure 1).
Figure 1: Resonance condition in a machine
Resonance can be prevented by checking that the machine does not operate at frequencies close to the natural frequencies of the machine structure. Alternatively, the system can be modified by changing its mass or stiffness; this will shift the resonant frequency higher or lower so that it is no longer close to the operating frequency. In some cases you may also use tuned dampers that damps out vibration. If left unchecked, resonance can excite the structure and lead to failure.