Ashraf N., Talbot C., Fieldhouse J.

The work incorporated in this paper is to design and develop a test rig to apply a range of pressure both along the length of the pad and radially and then investigating the effect of different hydraulic pressure on interface pressure distribution between the pad and the disc. The tests include static pressure measurements with the film between the pad friction face and the disc the centre of pressure being adjusted using the master cylinders to provide a 'system benchmark'. The brake uses a 12 piston opposed calliper arranged to allow a number of the pistons to be controlled independently using 4 master cylinders. This allows the interface centre of pressure to be adjusted both along the length of the pad and radially. The work also includes both analysis and practical applications of successful noise fixing through the consideration of pressure distribution and centre of pressure. The paper concludes with continued work to measure the dynamic pressure using above approach with the pressure sensitive film being embedded within the friction material. This modified pad is first 'calibrated' to the static interface pressure measurements by progressively reducing the effective depth of the film from the rubbing face. The test procedure replicates the process, and values used, for the static interface measurements. Once the static characteristic behaviour and sensitivity of the modified pad is established, it is fitted to the brake and the centre of pressure variation measured under dynamic conditions. This allows the movement of the centre of pressure to be plotted against brake pressure and rotor speed. The dynamic centre of pressure is then varied during braking using the master cylinders. This allows the relationship between its position and noise propensity to be established.