Acoustic energy transfer by friction induced vibrations

Friction-induced vibrations are often investigated for their unwanted effects, such as surface wear and dynamic instabilities. This article focuses on the exploitation of friction-induced vibrations to transfer the energy between different acoustic fields by an interface under frictional contact. One of the main possible applications is the use of the generated acoustic field for passive structural health monitoring (SHM). A mechanical device (secondary acoustic source, SAS), able to perform the energy transfer, is here tested on a simplified benchmark. The energy transfer is obtained between two vibrational fields: a primary field, which is the ambient acoustic field on the structure and is generated by a known source, and a secondary field with a different frequency content produced with the developed device by friction-induced vibrations. The test bench analyzed in this work is composed by a main structure, which is excited by the primary (ambient) acoustic field, and the SAS, able to absorb part of the acoustic energy of the primary field and radiate it within the secondary acoustic field. The device is composed by a main resonator, excited by the primary acoustic field, in frictional contact with a secondary resonator to provide a broadband secondary acoustic field. The objective of the article is to analyze and estimate the power flows from the main structure to the SAS and vice versa, within the two acoustic fields.