Thermal and material characterisation of coated lightweight disc brake rotor

Environmental concerns linked to CO2 emissions have placed the automotive industry under considerable pressure to reduce the carbon footprint of the vehicles that they produce. One way forward involves the use of alternative lightweight materials. The use of aluminium alloy in a brake rotor has the potential to save around 20kg in unsprung mass on a medium sized passenger car. A full scale prototype lightweight coated ventilated aluminium alloy (6082) brake rotor was manufactured to investigate the thermal performance under drag brake test conditions. The brake rotor’s rubbing surface was coated with alumina layer using a plasma electrolytic oxidation (PEO) process. The ventilated brake rotor geometry contributes to the ability of the structure to dissipate heat through the inclusion of an array of appropriately configured vents and so has further bearing on the ability of the rotor to run cool. It is also feasible to explore the impact of vane design on the cooling of the rotor since the vented section of the rotor can be easily reconfigured using the current prototype. Experiments were conducted using a brake dynamometer. Brake rotor rubbing surface temperature, hydraulic pressure, rotational speed and brake torque were monitored during the test. The coefficient of friction was found to be around 0.5. Abaqus software was used to generate a three dimensional finite element model of a section of the coated brake rotor. The simulation results were found to be in good agreement with the experimental results when a heat transfer coefficient of 30 W/m2K was specified on all free surfaces. It was shown that coating thickness has a minimum effect on the substrate temperature. In parallel, a wear analysis has also been carried out using a pin-on-disc experimental setup. The mass of the friction material and the small discs were measured before and after the test. The wear coefficient for both conventional grey cast iron (GCI) and coated aluminium alloy were also measured and compared. It was found that wear rate of the PEO coated disc is about 15 times lower than the GCI. The wear rate of the friction material when run against the PEO coating was about 5 times less than when the same material was run against cast iron, even though the friction coefficient was on average higher (0.6 of 0.5)