In this research, the tribological and dynamical characteristics of a brake pad with multiple blocks are investigated using experimental and numerical methods. A dynamometer with a multiblock brake pad configuration on a brake disc is developed and a series of drag-type tests are conducted to study the brake squeal and wear behavior of a high-speed train brake system. Finite element analysis is performed to derive physical explanations for the observed experimental phenomena. The experimental and numerical results show that the rotational speed and braking force have important influences on the brake squeal; the trends of the multiblock and single-block systems are different. In the multiblock brake pad, the different blocks exhibit significantly different magnitudes of contact stresses and vibration accelerations. The blocks located in the inner and outer rings have higher vibration acceleration amplitudes and stronger vibration energies than the blocks located in the middle ring.
This study experimentally investigated the influence of angular distribution of a grooved surface on wear properties as well as friction-induced vibration and noise characteristics. The surfaces of brake disc material were modified by cutting grooved surfaces with different angular distributions. The differences between the grooved and smooth surfaces in friction and wear and friction-induced vibration and noise were evaluated. This was performed via a pad-on-disc test configuration where the brake pad material was used as a counterface. The test results indicated that all the grooved surfaces with different angular distributions had significant potential in improving friction and wear behaviors of the contact surfaces and also in reducing the amplitudes of high-frequency vibration accelerations and noise pressure levels. Additionally, the results indicated that the ability of the grooved surfaces to suppress the generation of noise is closely related to the angular distribution of the grooves and the interference length of the grooved surfaces on the contact interface. The grooved surface allowed for entrapping and exhausting wear debris from the contact interface, which improved the wear status, and this was one of the reasons for the noise reduction of the grooved surface to a certain extent. Meanwhile, another reason was that the grooved surface interrupted the concentrated contact pressure and changed the contact pressure distribution on the leading edge of the contact surface.
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