| The NVH characteristics of automobile brake system concern the characteristics of the whole vehicle NVH,and the poor brake NVH characteristics will bring a large number of complaints from consumers,since most of the front and rear wheels of passenger cars are made of disc brakes,so it is of great significance to study the NVH characteristics of disc brakes.In this paper,the front axle floating clamp type brake of a passenger car is selected as the research object,according to the characteristics of brake structure,a six-DOF dynamic analysis model is proposed.Based on the theory of complex eigenvalue analysis,the factors affecting the stability of the system are analyzed in detail and the influencing factors are analyzed concretely.A prediction model of squeal noise in brake system is established by combining finite element complex eigenvalue modal analysis and noise bench test.It is proposed that the occurrence rate of brake squeal noise can be reduced through the design of brake backplate slotting and insulator multi-layer structure,and the NVH characteristics of brake system can be improved.Combining the prediction model with the noise bench test,the effectiveness of the proposed noise reduction method is verified and the noise reduction mechanism is analyzed.Through the mechanical analysis of the brake system,it is found that the asymmetry of the brake pressure distribution will affect the stability of the system,and a new structure caliper is proposed,and the simulation and test show the effectiveness of the improved structure.Firstly,a three-dimensional model is established in CATIA,the mesh is divided and the properties such as materials are defined by HyperMesh,and then the model is imported into Ansys/Workbench for real modal and complex modal analysis.The validity of the key components finite element model is verified by the real modal experimental analysis.Then the APDL commands are written in Workbench to calculate the complex mode of the system,and the results show that the system there are seven unstable modes in the system.The results are in good agreement with the noise bench test results,which shows that the model can predict the occurrence of squeal noise well.Secondly,through the dynamic analysis model of six-DOF brake system,it can be seen that the brake backplate and insulator are the two key components that affect the stability of the system.It is found that the setting of transverse grooves on the surface of brake backplate is beneficial to the stability of the system through trial-and-error method,and the simulation results show that the braking backplate with three transverse grooves has good effect,and then simulation results are verified by the bench test.Furthermore,a multi-layer structure insulator is proposed to improve the squeal noise of the system,and four kinds of insulator of the structure form are designed for complex modal calculation,and finally the type IV insulator(rubber-steel sheet-rubber)is found to reduce the overall noise incidence from 19.27% to 1.27%.Finally,through the analysis of the mechanical model of braking system,it is found that the unbalance of braking pressure on the brake disc will affect the stability of the system,so the innovative design of the caliper structure,simulation and bench test results show that the design of the new structure caliper can greatly improve the stability of the braking system and reduce the occurrence of squeal noise.The overall noise incidence can be reduced from 19.27% to 3.63%,and the characteristics of contact pressure distribution are analyzed by simulation and the beneficial effect of the new structure caliper is compared and analyzed by road test. |
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