Abstract
KEYWORDS – brake disc , ceramic MM composite , axle and wheel brakes , unsprung masses , High Speed Trains
ABSTRACT - The Aluminum Metal Matrix Composite Brake Discs seems to be a very promising technological solution to give a strong and credible answer to the double request for Low Weight solutions and low Life Cycle Cost during the full service life of the Friction Pair constituted by a Brake Disc and the Pads acting on it , for different Railway applications . Starting from 2005 the ZheJiang Tianle Group has been developing this new process to produce a real breakthrough solution for the Rail Brake Discs and has been actively testing the new product. The innovative Concept is based on the use of a high Temperature and low Wear Material (like the SiC Foam ) filled with a metal alloy , able either to fully penetrate and fill the MM Foam and to transmit , with a very high flow rate , the heat produced on the friction surface . The air flow, cooling the internal part of the disc, is contributing to reduce the initial thermal shock and also to stabilize, at lower level, the stationary temperature, during prolonged brake applications, thanks to a better heat flow , “discharging” the energy from the friction surface . The SiC Foam is placed on the external faces of the disc to be casted , then all the volume of the disc is filled with a special low pressure die casting process , through the injection of the Al alloy . The result is a noticeable reduction of the total weight ( up to -60% , compared to a conventional steel disc of similar performances !); the average density of the Al MMC brake Disc is around 2.8 Kg/dm3 . Performances : this new technological solution is suitable for services requiring either frequent brake applications , like on the urban, metro and commuter lines, or HS Trains as it has been also tested up to 350 Km/h, with top speed tests up to 380 Km/h and max temperature below 500°C with a resulting friction coefficient (mu) of between 0.4 and 0.3. Other tests at 160 Km/h, starting from a Temperature of 50°C, in about 43 sec , has shown a max Temperature of < 200°C . Weight : the heavy reduction of the weight of this new technology can have a deep impact on all the economical performances of a train . For example an HST with three Discs per axle, thanks to the reduction of at least 50 Kg per Disc, can get a total reduction of 300 Kg per bogie. This corresponds to more than 3 paying passengers per trip or at least 6 more tickets sold per day ! Even considering a very low fare of 30/35 € , it means an higher income of 200 € per day per bogie !