A brake works by converting kinetic energy into
heat. When all of the kinetic energy is converted the
vehicle is stopped and the brakes are hot. Problems can
arise due to melting of the wheel surrounding the brake,
boiling of the hydraulic fluid and fade of the brake
material. Secondary problems arise due to excessive wear
and noise generated during a stop. These secondary problems
usually are not life threatening; however, their treatment
represents huge warranty costs. Research carried out
at the Center for Advanced Friction Studies at Southern
Illinois University (EEC-9523372) has led to isolation
of many of the materials-dependent sources that contribute
to such problems. One finding is that noise in automobile
brakes can be generated by the formation of a layer of
material on the surface with characteristics different
from the bulk material. To address this problem, Center
researchers found that the properties of this “friction
layer” can be tailored using “smart”
criteria. Combining different metallic oxides with amorphous
carbon can completely eliminate any noise. In addition,
noise and vibration of carbon-carbon aircraft brakes
can be controlled by heating the friction material to
temperatures that convert all carbon containing materials
to solid carbon with no remaining carbon free radicals.
In automobile brakes, the constituents present in the
friction layer sensitively control wear. Balancing the
content of metals and solid lubricants can eliminate
any large adhesive forces that might be generated between
the rubbing surfaces.
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