Thermal performance of peo coated lightweight brake rotors compared with grey cast iron

Brake rotors play a significant role in converting the vehicle kinetic energy into heat energy that is dissipated through conduction and convection. The automotive industry has been looking for many years to develop lightweight brake rotors to reduce vehicle weight and subsequently improve fuel efficiency and vehicle emissions targets. Uncoated wrought aluminium alloys and metal matrix composite (Al-MMC) rotors have been reported to have insufficient safety margin for most passenger car applications. In this study, the thermal performance of coated and uncoated lightweight aluminium disc brake rotors was investigated numerically and experimentally, using both small scale and full size brake dynamometers. Five small scale solid brake rotors were investigated: grey cast iron, forged aluminium alloy (6082), the same 6082 alloy but with an alumina surface layer applied by plasma electrolytic oxidation (PEO), cast aluminium MMC (AMC640XA), and the same MMC again with PEO alumina surface layer. The disc and pad temperatures, brake pressure, coefficient of friction and brake torque were monitored during the tests for each disc brake material. In addition, a two dimensional axisymmetric finite element model was developed using Abaqus software in order to investigate the temperature distribution through the disc. The 2D FE model demonstrated good overall agreement with the experimental results and showed the same general trends. It was found that the PEO coated aluminium alloy has the best overall performance of the lightweight rotors tested in terms of friction and structural integrity at elevated temperature.