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Creep groan is a low frequency noise generated by the stick-slip phenomenon that occurs when moderate brake pressure is applied between the surfaces of the brake disc and brake pad in a low-speed vehicle. It generally occurs when a vehicle is starting to move from a complete static condition or as it slowly comes to a stop when driving. Transfer path analysis (TPA) is a technique than not only provides a methodical approach to trace the flow of vibro-acoustic energy but also allows users to analyze structure-borne noise contributions. Thus, TPA is extensively used to scrutinize creep groan. The primary purpose of this paper is to empirically identify and evaluate the influences of the environmental conditions, chassis system, and brake material on creep groan using the TPA technique. Once the route that contributes the most vibro-acoustic energy from the source to the receiver is identified through TPA, a mass is added on that specific path to observe the changes in creep groan.

The effects of pad properties and thermal coning of discs on high speed judder were investigated using dynamometer and vehicle tests. The friction materials of different thermal conductivities were manufactured and the discs were design-modified to control the thermal coning during braking under high speed conditions. Brake Torque Variation(BTV) was measured to evaluate the judder propensity in the dynamometer tests and the vibration on steering wheel and brake pedal was measured in the vehicle tests. The results showed that the increase of thermal conductivity of pad could not affect the judder propensity during high speed braking below 350°C of disc temperature, however better disc design reduced judder propensity due to the lower thermal deformation. Moreover, the increase of pad compressibility can reduce judder propensity due to the increase of damping capacity.