A stick slip model of the singing wineglass

The characterization of friction is a multiscale problem involving a balance between asperity contact and fluid film forces. Periodic stick-slip phenomena are often associated with the friction force that causes mechanical vibration. This type of vibration can cause noise to radiate via structural modes of the system. Many mechanical systems have connections that involve friction, including bolted joints, bearings, and brakes. Avoiding stick slip conditions minimizes wear and vibration, while extending the life of the component. Understanding the exact conditions that stick slip occurs can be difficult, as it requires a characterization of the friction forces and the loss mechanisms in a complex mechanical system. Classic single degree of freedom models predict the stability criterion to be a function of the system damping, normal load, and the derivative of friction coefficient with respect to sliding speed. Many musical instruments utilize the stick slip phenomenon to produce sound. In this work, we study the stick slip phenomenon with a singing wineglass. The dynamic friction force and radiated pressure is measured under a variety of speed and load combinations. Friction models of increasing complexity are used to demonstrate the main features of the dynamic force and radiated pressure spectra.