The Effect of the Macroscopic Contact Surface Status Caused by the Uneven Wear on Friction Induced Vibration


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Research and /or Engineering Questions/Objective: Friction induced vibration (FIV) and wear are the inevitable phenomenon in a brake system, which could be the source of discomfort for the passengers, also shorten the service time of brake system. Nowadays, numerous researchers have investigated the FIV of the friction interface and the wear evolution of friction pad, however, the knowledge about the effect of wear status on the dynamic behaviour of brake interface is lacked as well. Considering that a real brake pad would have various wear status which can exhibit different dynamic behaviours, therefore, a numerical and experimental investigation is performed to reveal the relationship between wear status and dynamic behaviour.

Methodology: A series of experiments is performed in a small-scale friction dynamometer to observe the evolution of wear status and dynamic behaviour. A detailed three-dimensional finite element (FE) model is created based on the friction dynamometer. Additionally, a wear model, in which the mass loss of unit contact area is proportional to frictional work per unit area between the pad and disc, is developed to shed light on the dynamic behaviour of the friction pad related to the wear status. Finally, a lumped parameter model is used to aid the understanding of the mechanism of wear status’ effect on the dynamic behaviour.

Results: The friction induced vibration is observed and the intensity of FIV is increased with the wear process, and an inclination and uneven wear are found on the pad surface and the maximum wear depth occurs at the positions close to the leading edge of pad surface. The established wear model can reflect the real wear behaviour of pad surface effectively. The experimental and numerical results show that the dynamic behaviour have a strong relationship with the wear status, the increased contact inclination angle of pad surface will lead a larger intensity of FIV.

Limitations of this study: Applying the findings to practice system is still under studied since a real brake system is much more complex comparing to the small-scale dynamometer.

What does the paper offer that is new in the field in comparison to other works of the author: A numerical wear model is established and the effect of wear status of pad on the dynamic behaviour is investigated numerically and experimentally. The obtained results are beneficial for understanding the relationship between the wear and dynamic behaviours.

Conclusion: A small-scaled pin-on-disc experiment is performed with the real brake material, and a contact inclination angle is found which increase with the wear process. A corresponding FE and wear model are established to investigate the mutual effect between the uneven wear and contact pressure. The analysis of transient dynamic and lumped parameter model indicate that the increased contact inclination angle will cause the heavy torsional vibration in the tangential which strength the coupled vibration in normal and tangential.

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