What are harmonics in the context of vibration analysis?

Harmonics are defined as integer multiples of the fundamental frequency in vibration analysis. The fundamental frequency is the lowest frequency at which a system vibrates, and harmonics occur at regular intervals above this frequency. For instance, if the fundamental frequency is 10 Hz, the first harmonic would be 20 Hz, the second harmonic would be 30 Hz, and so on.

Understanding harmonics is crucial in vibration analysis because they can indicate specific issues within a mechanical system, such as imbalance, misalignment, or other forms of mechanical distortion. By analyzing the harmonic content of a vibration spectrum, analysts can diagnose problems more effectively and implement appropriate corrective measures.

In contrast, the other options describe different aspects of vibration or noise, which do not directly pertain to the definition of harmonics. Fractional parts of the main frequency refer to subharmonics, and random components of noise are unrelated to the systematic nature of harmonics while irregular fluctuations pertain to non-periodic movement rather than the predictable nature of harmonic frequencies.