Abstract
Actual axle mounted brake discs for high speed trains are made by casting with a subsequent heat treatment to generate the required mechanical properties. The casting process is connected with a number of disadvantages. From the technical point of view, there is a high scrap rate of approximately 40 % which is mainly caused by casting defects, like hot cracks, non metallic inclusions, porosities or cavities generated during solidification of the moulding mass. The scrap rate as well as the heat treatment of the brake disc lead to high total manufacturing costs (TMC). Moreover, the reproducibility of the casting process is poor, which results in high differences in the quality of the brake discs. Finally, the development of new or modified brake disc designs is a long-term process since first samples have to be produced. To avoid these commercial and technical disadvantages, Faiveley Transport developed an innovative ventilated, modular axle mounted brake disc. This disc is built by steel sheets, which are the friction layers, with spacers in between. The contour of the friction layers is produced by laser cut. By applying electron beam welding, all single parts are joined in a hybrid structure. By using materials for the friction layers and the spacers, which are produced as bulk good, TMC as well as the delivery time can be significantly reduced. Furthermore, another advantage of the innovative concept is the high flexibility of the design. Referring to the friction layers and spacers a wide range of materials can be used in order to fulfil specific requirements of different applications. In order to evaluate the wear behaviour of the friction layers under equal conditions, different steel grades have been selected and were tested on a scale rig. Compared to standard brake disc cast steel grades, a number of materials with a significant reduced specific wear rate could be identified. In addition to this, full scale prototypes have been tested on a test bench in order to evaluate the performance under emergency and service conditions on high speed route profiles.
KEYWORDS - Axle mounted brake disc, modular ventilated disc, high speed train, friction material