Impact Analysis Of Shim Structure Parameters On Disc Brake Squeal

In recent years,with the advanced development of the automobile industry and comfortable request from consumers,the automobile manufacturers and suppliers have paid attention to NVH performance.The brake squeal is an important part of the NVH performance of the brake system and it has a great influence on the human body and environment.Reducing and inhibiting the squeal noise has become a significant issue to be handled during the process of brake development.This paper chose a front disc brake system as the research object and analyzed from the noise propagation route by combining the finite element complex modal simulation analysis and the NVH bench test.This paper was aimed to figure out the influence of shim parameters(material structure,material thickness and shape)on squeal noise,propose an optimal noise reduction scheme and verify the feasibility of the noise reduction scheme according to the road test.The disc brake geometries were modeled in CATIA and finite element mesh was modeled in Hypermesh.The free modal analysis of the parts was performed by using the modal and harmonic response module in workbench,and verified the accuracy of the model by the FRF test.Then the complex modal analysis of the brake system was performed after setting up the connections,constraint conditions and loads.The NVH bench tests were performed on the LINK 3900 dynamometer and the test result of the brake pad without slotting,chamfering and shims was set up as the noise matching baseline.Using the synchronous and comparative analysis of finite element simulation and noise bench test,an optimized brake pad was updated both in complex modal analysis model and bench test to figure out the unstable modal frequency and finish the noise test.Rubber thickness,steel thickness,shape of rubber-steel and rubber-steel-rubber structure of shims and chamfer dimension were analyzed in turn to conclude its effects on specific frequency noise.The results showed that: the lower rubber thickness can effectively suppress low frequency squeal at 1.8kHz;the overall noise reduction performance of rubber-steel-rubber structure shim was better than rubber-steel structure shim;the higher steel thickness can inhibit the instability of the brake system.The final scheme of rubber-steel-rubber structure shim and 15 mm chamfer reduced the noise occurrence from 19.9% to 1.27%,which was obviously effective.Distinguished from other scholars,road test was performed innovatively.The final optimal scheme of brake pads was assembled on the vehicle and finished the noise road test in Yellow Mountain with a total of 20000 km.The performance of this scheme was verified in application through subjective evaluation and objective data collections.Finally,the whole work of the research was summarized and the conclusions were drawn.Meanwhile some expectations were put forward on further investigation according to the existing deficiencies.