Study On Closed-loop Coupling Model Of Disc Brake Noise

Braking performance plays a more important role with the development of automotive technology and the increase of running speed. If the brake system structure is not well designed, or the friction material is worn, or the braking condition changes, strong vibrations and noises may appear during the braking process, which effects the component fatigue life, riding comfort and safety. So analyzing brake system NVH accurately and eliminate the problem effectively are not only valuable for engineering practice, but also for accademic researches.Complex eigenvalue analysis using closed-loop coupling model is an effective method in brake squeal research. A closed-loop coupling model of a sample noisy disc brake system, with 300 degrees of freedom and 27 k Hz cut-off frequency is built. During the modeling process, substructure modal parameters and coupling interface parameters, are two key points which influence the accuracy of the model.As for treatment of substructure modal parameters, based on the vibration theory, expressions of "pure" rigid body modes of pads and “synthesized” disc rotor repeated-root modes composition coefficient are derived. They are used to modify brake pad and disc modal parameters calculated through the finite element method, to reach a good consistence with the practical conditions; Finally the substructure mode composition method is used to find the key modes of pads and disc rotor to influnce braking squeal tendency.Study on substructure coupling interface parameters, contains extraction of coupling interface stiffness and dynamic friction coefficient. The secondary coupling interface stiffness values are extracted through empirical method. Non-linear optimization method is used to minimize the errors between model calculation and stationery modal test, thus the critical coupling stiffness values reach a better approximation of real situations; For dynamic friction coefficient, a reasonable value is obtained from tests and theoretic analysis. Finally, the coupling interface parameters are adpoted to closed-loop coupling model for complex eigenvalue analysis, the comparison of brake squeal bench test results with model prediction shows better consistency than that with initial parameters. The effect of brake-line pressure on interfacial coupling stiffness and brake noise tendency are also studied using the same method.Through the presented work, the modeling methodology of closed-loop coupling model is more integrate, more normalized and more systemized. The accuracy of model prediction is greatly improved. This will provide a solid base to analyze brake squeal problem and adopt noise eliminating solutions effectively.