The Analysis And Optimization Of Drum Brake Instability

The drum brake is an important component to ensure the vehicle's safety.The main part of the drum brake are drum,brake plate,brake shoebrake shoe and the corresponding friction linings.If the brake design is not reasonable,it will be in an unstable state in the braking process,resulting in severe vibration and radiate noise,especially high frequency scream.When traffic is heavy,the automobile brake will happen at any time.The brake noise will not only affect the comfort of occupants,but also pollute the environment.The research on brake noise is mainly concentrated in the study of disc brake at present.However,the brake noise generated by the drum is also very serious.Therefore,it is necessary to study the instability of drum brake,and then to study the problem of noise.This paper takes an enterprise provides automotive drum brake as the research object,the factors of instability and its influence were analyzed and optimized.First of all,constructed four degree of freedom vibration model of the contact element of drum brake according to the working principle of drum brake.Coupling of friction leads to asymmetry of stiffness matrix,the system appears complex eigenvalues.The real part show that mode is not stable.Based on this theory,the nonlinear finite element model of the friction between the brake drum,the brake shoe and the friction lining is established,and the simulation shows that the unstable mode of the brake is mainly concentrated in range of3500 Hz,4900Hz,6200 Hz,10500Hz,11200 Hz,11900Hz,12800 Hz,13500Hz and14600 Hz.The NVH test of brake results show that the frequency of the occurrence of brake noise basically includes unstable modal frequency,and the occurrence degree of noise is corresponding with real size of the unstable mode.The model is proved to be effective.Secondly,taking the coefficient of instability as the evaluation parameter.Based on the nonlinear finite element model of the brake,the influence factors of instability are simulated.The results show that the friction coefficient,the contact area and the elastic modulus of shoe and linings are significant and nonlinear,and the influence of the elastic modulus of the drum is relatively small,but also nonlinear.The braking pressure has little influence and is linear,and drum speed almost no effect.Finally,nonlinear influence factors including the friction coefficient,the contact area and the elastic modulus of the brake drum,brake shoe and friction lining are taken as the design variables and the stability coefficient is taken as the design objective.Response surface methodology was used tooptimize.Combined with the range of each factor,the optimization scheme is that the friction coefficient is 0.35,the contact area is 90% of the total area,The elastic modulus of the brake drum is 1.33 GPa,the elastic modulus of the brake shoe is 2.15 GPa,the elastic modulus of the friction lining is 369 MPa,and the coefficient of instability is reduced by55.4%,compared with the original model.Instability of drum brake has improved significantly.The results show that the application of finite element method and response surface optimization method in the study of drum brake instability has engineering value.It can be used as reference for the design of the brake or the improvement in order to reduce noise.