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Wear-Induced Migration of Hot Bands: Models and Comparison with Experiments
Abstract:
Although the radial migration of hot bands has been frequently observed, a systematic investigation of this phenomenon has not yet been performed. The ring-shaped temperature maximum, which occurs on the brake disk, is undesirable because the focused temperatures destroy the local materials in contact. Moreover, a hot band carries a dominant portion of the frictional load. If a hot band moves radially, the braking torque is directly influenced. It is supposed that material wear influences the radial hot band migration.
New models demonstrate that wear is indeed the mechanism that triggers hot band migration. First, a minimal model including thermal expansion and a load-dependent loss of material is introduced. The simplicity of the model allows for an understanding of the impact of wear, as well as the mechanisms that lead to a periodic load distribution. This model can be analyzed in terms of complex eigenvalues, showing a periodic load distribution in the sliding plane. In fact, in some parameter cases, a nonlinear evaluation reveals hot band migrations that an eigenvalue analysis fails to predict.
Secondly, the minimal model is replaced by a model with many degrees of freedom, which is parameterized with respect to an example brake system. A numerical study shows how a hot band migrates periodically inwards and outwards over the disk, leading to braking torque fluctuations. A comparison between the model and experimental results shows quantitative agreement with respect to the amplitudes and frequency of brake torque fluctuations and operating points, where hot band migration occurs.