The Importance of Pad Aspect Ratio in the Thermal Analysis of a Reduced Scale Brake

The performance of a brake system can be assessed in its early stages through reduced scale testing. An established scaling methodology was used in this study to scale the brake pads based on constant energy density. The primary aim was to investigate the impact of the aspect ratio of a scaled brake pad on the thermal characteristics of a scaled disc during drag braking conditions. Brake pads with four different aspect ratios were used against the scaled disc and these were scaled relative to the brake disc and pads of a medium sized passenger car. Using relevant scaling relationships, a speed–pressure matrix, consisting of nine tests, was derived and utilised in the experimental analysis. The tests were conducted using a conventional brake dynamometer. Temperatures were measured using thermocouples on the disc and pad and, for specific tests a thermal imaging camera was also used. The experimental results showed that a strong dependency exists between the maximum rotor temperature and the pad aspect ratio. This suggests that consideration of pad aspect ratio be reflected within the scaling process. A relationship between the circumferential and radial dimensions of full scale and reduced scalebrake pads was established based on their measured thermal performance. The experimental results were also used to validate a finite element model of the system. This was subsequently able to highlight important limitations associated with the model that apply equally to simulations of full and small scale brakes.