High frequency noise has been observed during reciprocating sliding of metal-metal dry contact. In tribology, the study of friction and wear, this noise was historically associated with “brake squeal;” however, it has also been found to occur within structures and systems that experience high frequency, reciprocating contact of metal constituents; typically found in the connecting locations such as the joints of a variety of jointed structures ranging from automobiles, airplanes, and HVAC systems. This type of tribological behavior has been replicated in tribology experiments where researchers found that noise is only produced during the tension phase of the fretting cycle and only occurs when specific criteria are met in the fretting system: reduction in the coefficient of friction and the self-excited vibration of the structure. In this study, two 304 SS steel samples are tested within a fretting rig apparatus that produces audible noise. In addition to the spectral analysis of the noise produced, a new metric, the Total Harmonic Distortion (THD), more commonly associated with assessment of fidelity in power systems, is introduced as a means of providing a real-time measure of the fretting system’s dynamics during experiments.

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