Dr. Qianjin Yang, Yantai Winhere Auto-Part Manufacturing Co., Ltd., CHINA
Mr. Fulin Gai, Yantai Winhere Auto-Part Manufacturing Co., Ltd, CHINA
Ms. Hui Yu, Yantai Winhere Auto-Part Manufacturing Co., Ltd, CHINA
Mr. Liqiang Song, Yantai Winhere Auto-Part Manufacturing Co., Ltd, CHINA
Mr. Baozhi Zhang, Yantai Winhere Auto-Part Manufacturing Co., Ltd, CHINA
Research and /or Engineering Questions/Objective: Brake discs’ geometry plays a significant role in brake judder issues; especially, the Disc Thickness Variation (DTV) has been verified as one of the main causes for the cold brake judder. Recently, in vehicle tests for the performance verification purpose, it was observed that the brake discs with variable friction plate thickness were prone to the hot judder issue, even the brake discs met the technical requirement on the overall DTV. A request was then raised to study the relationship between the variable plate thickness and the observed hot brake judder issue; and to find the solution to alleviate the corresponding brake judder issue. This paper reports the simulation studies carried out thereafter, and the results achieved towards these objectives.
Methodology: In these studies, Finite Element Analysis (FEA) method using a 3D full model of a ventilated brake disc is employed, in which the piston, the inner and outer brake pads are also modelled together with the brake disc; and the loadings and boundary conditions for all the components are defined as close to reality as possible. In order to isolate the effect of the variable friction plate thickness, comparison studies have been conducted, in which the disc with a sinusoidal variable plate thickness is analysed together with the same disc but with a perfect uniform plate thickness under an emergency braking condition.
Results: In the comparison studies, the temperature and the out-of-plane displacement at some typical locations on the inboard and outboard friction surfaces of the disc in radial and circumferential directions are examined first. Then the dynamic lateral runout, and the coning of the inboard and outboard friction surfaces are characterised. Finally, the braking torques are compared. It is found that the variable thickness of the friction plates does change the temperature distribution, the out-of-plane displacement and the dynamic lateral runout of both the inboard and outboard friction surfaces. However, due to the same overall plate thickness, the dynamic DTVs of the disc are similar for the two cases, and the differences of the braking torques are also very small and can be neglected.
Limitations of this study: In current studies, the caliper is not modelled. It is anticipated that the deformation of the caliper under pressure will change the contact pressure distribution between the pads and the disc, and the temperature generated in the brake disc, as well as the deflection of the disc under the combined thermal and mechanical loadings. However due to the overwhelming complexities in such a fully coupled thermo-mechanical simulation, it has not been attempted to include the caliper in the studies.
What does the paper offer that is new in the field in comparison to other works: In this paper, for the first time as the authors are aware of, the brake disc with a variable friction plate thickness is analysed thoroughly, and its effects on the disc judder performance under the emergency stopping condition are identified.
Conclusion: The comparison studies in this paper show that the variable plate thickness incurs a significant variations of the lateral run-out and the coning for the disc under an emergency stopping condition when compared with the case of the uniform plate thickness. However, the variable plate thickness has not much effect on the dynamic DTV and the BTV of the disc under operation. Therefore the excessive lateral run-out and the coning in the form of the first order waviness from the variable plate thickness are likely the cause behind the hot judder issue observed in the road tests. Dynamometer tests to verify this conclusion are planned, in which specially designed brake discs with variable friction plate thickness will be tested while other factors affecting the brake judder will be controlled and minimised. If it is verified, corresponding attention to the variable plate thickness of the brake disc will be paid in manufacturing process.