METHODS

The basic principle here is the lack of internal sta bility of a rotating disk at a motionless counterbody [6]. Essentially, a frictional disk pressed against a motionless counterbody by an axial force is initially at rest. In other words, this open system does not acquire energy from outside.

However, if energy (rotation) is transmitted to the disk, it is displaced practically instantaneously, on account of unbalanced tangential force. As a result, the disk begins to perform circular radial self oscilla tions, at a frequency considerably exceeding its rota tion frequency. Analysis of the differential equations describing this motion indicates that all the trivial solutions of the system are unstable. This may be char acterized as soft excitation of vibrations and may be regarded as an expression of the principle of minimum dissipation (energy scattering)[7].