Brake Groan Noise Investigation and Optimization Strategy for Passenger Vehicles

Groan is a low frequency noise generated when moderate brake pressure is applied between the surfaces of the brake disc and the brake pad at a low-speed condition. Brake groan is often very intense and can cause large numbers of customer complaints. During a groan noise event, vehicle structure and suspension components are excited by the brake system and result in a violent event that can be heard and felt during brake application. The cause of noise is friction variation of stick-slip phenomenon between friction material and disc. This paper discusses the approach for prediction and mitigation of brake groan noise for passenger vehicles having disc brakes. To identify the brake groan noise frequency, vehicle testing with operating condition for reproducing the groan noise is carried out and also impact frequency response analysis is performed to identify natural frequency of each chassis component like brake, suspension stud, lower control arm, knuckle etc. The finite element corner module plus sub-frame model with appropriate boundary condition is developed. Impact frequency response & modal frequency response simulation results are in good agreement with corresponding test results. The developed model is further utilized for the studying effect of various factors like suspension bushing stiffness, sub frame stiffness, add on mounting bushing for sub frame, stiffness of lower control arm, stiffness of carrier mounting area and stiffness of damper and addition of mass at various location on response frequency & amplitude. Based on ranking it is observed that combined higher stiffness of damper sub-assembly and strut top bush are potential solution to reduce brake groan noise.