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The noise induced by the rubbing of rough surfaces is not proportional to the contact area!

We realized an experiment to check if the friction noise of sliding rough surfaces is proportional to the contact area. We found that no! This result is not intuitive. A naive reasoning would states that the more numerous are the sliding solids, the higher is the noise they emit. Read more...

Experiment to measure the friction noise versus contact area.

A. Le Bot and E. Bou Chakra, Measurement of friction noise versus contact area of rough surfaces weakly loaded, Tribology Letters, vol. 37, p. 273-281, 2010.

A. Le Bot, E. Bou Chakra and G. Michon Dissipation of vibration in rough contact, Tribology Letters, vol. 41, p. 47-53, 2011.

The concept of entropy in statistical vibroacoustics

Up to now, statistical vibroacoustics and its main theory, statistical energy analysis, is entirely based on the application of energy balance. But if the analogy with thermodynamics is often underlined, it is never said what happens with the concept of entropy. We have discussed the second principle of thermodynamics in the framework of statistical energy analysis and introduced the concept of “vibrational entropy” and the “vibrational temperature” of sub-systems In steady-state condition, we have shown that the entropy exchanged with exterior by sources and dissipation exactly balances the production of entropy by irreversible processes at interface between sub-systems. Read more...

Statistical energy analysis for complex structures. Sub-systems behave like tanks for vibrational energy but also vibrational entropy. The first principle states the exchanges of vibrational energy between sus-systems and the second principle the exchanges of vibrational entropy.

A. Le Bot, Entropy in statistical energy analysis, Journal of the Acoustical Society of America, vol. 125, p. 1473-1478 , 2009.

A. Le Bot, A. Carcaterra, D. Mazuyer, Statistical vibroacoustics and entropy concept, Entropy, vol. 12, p. 2418-2435, 2010.

Statistical energy analysis is not a high frequency method!

It is usually claimed that statistical energy analysis is a high frequency theory of vibroacoustics. To check this assertion, we have applied the dimensional analysis to rectangular plates and we have identified four dimensionless numbers with which validity of SEA is defined: The mode count N, the modal overlap M, the normalized attenuation factor m and the coupling strength. It is found that in the frequency-damping plane, this domain is a narrow strip so that an increase of frequency with constant damping leads to get out the validity domain! Read more...

Validity domain of SEA in the frequency-damping plane.

A. Le Bot and V. Cotoni, Validity diagrams of statistical energy analysis, Journal of Sound and Vibration, vol. 329, p. 221-235, 2010.