Subsynchronous rub simulated in rotor kit with rubbing screw Rubbing occurs when rotating machine parts come into contact with stationary components. It is one of the most frequent malfunctions in rotating machinery, yet remains difficult to diagnose because vibration responses may appear as subsynchronous, synchronous, or supersynchronous (including harmonics). Accurate diagnosis requires a clear understanding of vibration characteristics, machine configuration, and dynamic

Torsional vibration is often overlooked in field measurements due to installation challenges, limited reliability of instrumentation, and complexities in signal processing. However, torsional effects can couple into lateral (radial) vibration through gear mesh interactions, making them observable in conventional vibration data. This paper discusses the manifestation of torsional–lateral coupled vibration, excitation sources, measurement methodologies, and modeling approaches,