Thermal Analysis of Mechanical Brakes in Rail Vehicles: Modelling and Simulation
Time: Fri 2025-12-05 09.00
Location: F3 (Flodis), Lindstedtsvägen 26 & 28, Stockholm
Video link: https://kth-se.zoom.us/j/63495040006
Language: English
Subject area: Vehicle and Maritime Engineering
Doctoral student: Yanjun Zhang , Fordonsteknik och akustik, Rail vehicle group
Opponent: Professor Philippe Dufrenoy, École polytechnique universitaire de Lille
Supervisor: Professor Sebastian Stichel, Fordonsteknik och akustik; Researcher Zhendong Liu, Fordonsteknik och akustik
QC 251111
Abstract
Rail vehicles are known for being energy-efficient in both passenger and freight transport. A critical subsystem of rail vehicles is the braking system, which ensures operational safety. Among the various braking systems, mechanical brakes are considered more reliable due to their fail-safe design, allowing effective braking even in the event of system failures - something that electric brakes today cannot guarantee.
Mechanical brakes generate braking force through friction, resulting in frictional heat and wear. The increase in temperature and wear of the friction pads, discs, or wheels induces uneven contacts. These uneven contacts introduce uncertainty in friction pairs and may reduce the coefficient of friction. Thus, friction heat affects braking performance and makes thermal analysis essential for mechanical brakes. This analysis primarily focuses on how heat is generated and dissipated. Conducting a precise thermal analysis of railway mechanical brakes is a challenging task.
While experiments are an effective means to investigate thermal characteristics, they are expensive and have limitations in data collection. In contrast, modelling and simulation are cost-effective and provide unique insights into thermal properties. This research focuses on modelling and simulating railway mechanical brakes with respect to their thermal-related properties. Three different modelling approaches are employed: analytical, numerical, and data-driven models. These methods aim to explore why composite brake blocks in winter result in longer braking distances, how to accurately simulate the temperature of brake discs, and what the computational cost is associated with each modelling method.
First, an analytical model examines how ice melts and is removed, revealing that the wettability of the composite material is the primary reason for the long braking distance of freight trains. The simulation results align with accident reports, which primarily occur at low ambient temperatures, around -15 °C, low speeds, approximately 20 km/h, and empty wagons. In the next step, a numerical model utilizes the finite element method (FEM) to solve heat transfer and elastic equations, incorporating thermal expansion, wear and contact. The simulation results are then compared with experimental data, demonstrating that this FEM model is robust, fast and accurate. Finally, a data-driven model is developed to reduce the computational cost of FEM. The results indicated that the data-driven model surpasses FEM in accuracy, computational time and complexity, with a root mean square error 12.1 °C vs. 23.4 °C, a computation time of 3 minutes vs. 104 minutes, and fewer input parameters, i.e. less than 20 vs. over 115.
In summary, this research employs modelling and simulation methods to conduct thermal analysis of the railway mechanical brake system, providing unique insights into thermal-related mechanical problems.