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New Component for Rail Brake Pads

In a stride towards advancing high-speed rail technology, researchers at the Powder Metallurgy Research Institute of Central South University in Changsha, China, have developed a solution to improve the performance of brake pads for trains operating at speeds of up to 380 km/h.

von | 27.05.24

This Shinkansen train is the latest 700 Series "N700 Supreme" introduced by JR Tokai Company in 2020 for the Tokaido and Sanyodo lines. It has excellent stability, quietness, and runs at a maximum speed of 285 km/h on the Tokaido and 300 km/h on the Sanyodo, © Kanenori/Pixabay
© Kanenori / Pixabay
Bullet Train

May 2024 | In a stride towards advancing high-speed rail technology, researchers at the Powder Metallurgy Research Institute of Central South University in Changsha, China, have developed a solution to improve the performance of brake pads for trains operating at speeds of up to 380 km/h.

Published in the Advanced Powder Materials journal, their study introduces sepiolite as a novel component in brake pads, replacing traditional graphite to enhance high-temperature adaptability and wear resistance.

The research team, led by Jiaqi Wu, focused on copper-based composite materials typically used with carbon-ceramic (C–C/SiC) discs, which are known for their robustness in high-speed braking scenarios. Traditional formulations have struggled with achieving a balance between low wear and high-temperature durability – crucial factors for ensuring the safety and efficiency of high-speed trains.

Preparation Flow Chart

Preparation flow chart of copper-based composite materials; (b) Preparation flow chart of C–C/SiC disc; (c) Schematic diagram of MM-3000 friction experiment; (d) Schematic diagram of 1:1 bench experiment, © Jiaqi Wu et al.

 

Exceptional mechanical and friction properties

The study reveals that replacing graphite with sepiolite not only enhances the mechanical properties of the brake pads by providing particle reinforcement but also improves their frictional performance. Sepiolite, a naturally occurring fibrous mineral, is known for its high-temperature stability and wear resistance, making it an excellent candidate for high-stress braking applications. The optimal addition of less than 6% sepiolite to the brake pads substantially increased the friction coefficient, crucial for effective braking.

One of the standout features of the new brake pad formulation is its ability to maintain stability under high temperatures – a common challenge in high-speed rail systems where braking components must withstand extreme heat without degrading. The researchers developed a multi-layered friction layer within the brake pads (outermost layer: a composite film consisting of B2O3, sepiolite, graphite, and metal oxide films; intermediate layer: metal oxide films), which plays a pivotal role in improving friction stability and wear resistance.

„Interestingly, the addition of sepiolite causes a change in the traditional saddle-shaped friction curve due to high temperature lubrication. Meanwhile, the primary advantage of sepiolite lies in its superior abrasion resistance, evident in the increased friction coefficient and altered wear mechanisms with higher sepiolite content. The wear resistance is optimal at 200 ​km/h (400 ​°C).“ state the authors.

 

Higher precision in maximum friction temperature prediction

Additionally, the team used advanced prediction models, including machine learning techniques, to optimize the performance of these brake pads under various operational conditions. Their findings indicate a significant reduction in wear rates and an improvement in heat dissipation, critical factors for prolonging the service life of braking systems in high-speed trains.

The successful implementation of sepiolite in brake pads could set a new standard for the industry, promising enhanced safety and efficiency for high-speed rail networks around the world. The implications of this research extend beyond railways, potentially influencing braking systems in other high-stress transportation modes such as automotive and aerospace, where safety and performance are paramount.

 

More information

Jiaqi Wu et al. (2024) Sepiolite: A new component suitable for 380 ​km/h high-speed rail brake pads in: Advanced Powder Materials, Volume 3, Issue 4, 2024, 100199, ISSN 2772-834X,
https://doi.org/10.1016/j.apmate.2024.100199 / open access.

 

(Source: ScienceDirect/2024)

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