Title: Effects of Brake Pad Boundary Contact Surfaces on Brake Squeal
text: The disc brake corner assembly is comprised of several subsystems (brake pad, caliper, rotor etc.) which have interfaces between two or more of these structures. The brake pad assembly as the subsystem connecting the rotor to the caliper has specific areas of contact which influence the onset and potential to control brake squeal. The primary excitation interface occurs between the friction pad and rotor surface. The contact is initiated by the piston apply force on the brake pad insulator. Contact interface reaction forces, displacements and deformations are generated and form the natural and geometric boundary conditions of the overall system. Brake squeal characteristics are strongly affected by these conditions. The study focuses on brake system dynamic response to interface contact conditions. The brake insulator and pad assembly interacting with the brake piston as well as caliper are evaluated. Modifications that change the system dynamics through these interfaces are also assessed by dynamometer testing. Properties including compliance, interface friction and traction, damping, decoupling and isolation are discussed with respect to their potential impact on mechanisms leading to brake squeal. Three practical solutions that have been proven to decrease brake squeal via interface modifications are demonstrated at two interface areas 1) Piston to insulator modifications via changes in friction level as well as decoupling and damping 2) Caliper assembly interface with the backing plate incorporating friction level changes with decoupling and damping at the attachment point. Comparative test results indicating the effect of these modifications are presented.