HOT BANDING WITH OSCILLATING RADII: MODELS INCLUDING WEAR AND TEMPERATURE

摘要

One type of thermoelastic instability in a brake system occurs as circular hot bands on the disk. Their appearance typically interferes with the observation of other thermoelastic instabilities, e.g. hot spots. The present investigation will focus on the phenomenon of such hot bands. Experiments demonstrate that they are usually not stationary, but slowly change their radial position on the disk, which leads to a nearly periodic brake moment on a timescale of minutes. We present a family of models that explain this observation taking into account elasticity, thermal expansion, thermal conduction and wear. A minimal model demonstrates how a thermoelastic instability can be partially stabilized, if surface wear is included. Different stability zones can be distinguished, including one where the load is periodically distributed between different contact areas. A nonlinear analysis covers the local loss of contact. Furthermore a discrete Multi-DOF-Model is introduced that describes the contact between brake pad and disk. In an instability regime hot bands periodically change their radial temperature profile on the disk. Highest amplitudes occur at the outer and the inner radius of the pad. The obtained stability zones, the frequencies and wavelength meet the results found by experiments. The presented model allows the investigation of the impact of single parameters, as well as principal mechanisms can be identified that must be taken into account when hot banding phenomena are modeled.