Damping Capacity of Pearlitic Gray Iron and Its Influence on Disc Brake Squeal Suppression

A major increase in damping capacity of pearlitic gray iron for brake discs has been obtained by modification of chemical composition. Car tests indicate that sufficient disc damping can be obtained to substantially reduce squeal tendency in disc brakes. The investigations showed that the frequency dependent damping is due to magnetoelastic and elastoplastic mechanisms at low frequencies. Apparently, the contributions from both mechanisms are enhanced by an abundance of large graphite flakes and a coarse pearlitic matrix microstructure. High carbon and silicon concentrations with minimal pearlite stabilizers are required. High damping capacity brake discs exhibited good braking characteristics and appeared significantly more wear resistant than conventional brake iron discs.