Brake Groan Noise Investigation and Optimization Strategies 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. Creep groan is the structure-borne noise that is related to dynamic characteristic of the vehicle. However, it has been mainly improved through friction material modifications in the past. In this paper, transfer path of creep groan noise was analyzed by means TPA and structural countermeasure to creep groan noise was suggested. This paper discusses the approach for prediction and mitigation of brake groan noise for passenger vehicles having disc brakes. For this purpose, a finite element system model consisting of brake corner module including sub-frame is modelled. Firstly, modal analysis is performed to ensure natural frequency results of individual components are in agreement with those hammer test results. Secondly, to replicate actual vehicle brake groan test condition impact frequency response analysis is performed with unit force is applied between pad-disk along with other appropriate boundary condition. Brake groan noise frequencies and transfer path simulation results are found to be in good agreement with corresponding test results. For brake groan noise optimization sensitivity analysis is carried out to analyze the effect of 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 brake groan noise frequencies and amplitude. Based on ranking of the obtained simulation results it is observed that combined higher stiffness of damper sub-assembly and strut top bush are potential solution to reduce brake groan noise.