Tricoherence for early contact detection

Premature contact between neighbouring structural components like coaxial tubes used in process plants and nuclear industry over a period of service is unacceptable. The detection of such a contact is important for the safe operation of the plant before an accident takes place. At an early stage of contact the structural components interact each other nonlinearly like a make and break when excited. Higher order coherences (normalized higher order spectra) are known to be a tool for the detection of nonlinearity in the signal, so these may be useful for the present case. An earlier work has used one of the higher order coherence (HOC), namely the bicoherence for the contact detection. The present study investigates the use of other HOC - the tricoherence in the detection of such an early contact between the two components. The results of a simulated example and an experimental example are presented here.