Mechanism And Simulation Analysis Of Brake Judder Of Vehicular Brake Disc

With the continuous development of the automotive industry, the demand for comfort and safety performance of the car is increasing. More and more people pay their attention on the NVH problem of the automobile. As a key part of automobile, the braking system not only affect the safe operation of vehicle, its stability during braking also has influence on the comfort of car, which makes it particular important. Recently, brake judder, a common malfunctions, which appears in low-frequency phase of braking system, attract more and more attention. However because of its complex factors, there are still many issues stay unresolved. Therefore, analysis on brake judder about its mechanism and factors was very important and has engineering significance.In this paper, the mechanism and transport path of brake judder are analyzed and a conclusion was made that brake torque vibration and brake pressure vibration are main source of brake judder. Through further analysis, it can be known that the brake toque is affected by uneven disc geometry and thermal deformation. As a result, this article do the research on factors of brake judder in two different directions, brake judder and hot judder. The specific work was did as follows:(1) A systematic process for the design of hydraulic brake systems is presented to analyze the influence on brake torque from each part of hydraulic system. Calculations of the brake torque and the vehicle deceleration are made when the driver apply a constant force on the brake pedal.(2) Set up a model of the uneven disc geometry, including disc thickness and side run-out. Transmit the uneven of disc geometry to the displacement of brake pad by using mathematic model. Simplify the brake system and establish Lagrange equation, using the displacement to calculate the brake torque vibration. According the model and the result, research how disc displacement and parameters between friction contact face influence discipline of the performance of cold judder. Then give a few improving measures to reduce the amplitude of brake torque fluctuation.(3) Set up the theoretical equation of friction heat fluxes and heat conduction, and establish thermo-mechanically coupled model by using ABAQUS software to analyze the temperature and stress distribution on the surface of brake disc when braking. Research the geometry changes of brake disc caused by the thermal deformation, and the accompanying vibration of brake torque. Concluded that hot judder is the result of combined effect from thermal deformation and friction coefficient.(4) Based on the result of finite element simulation, use a Plackett-Burman design to analyze the sensitivity how key parameters of ventilated disc influence the brake hot judder. According to result, a improved disc is promoted. Compare the thermo-mechanically coupled simulation of improved disc with that of the basic disc, it can be found that the improved has better thermal characteristic and smaller fluctuation of brake torque. Indicate that the sensitivity result can be applied to disc design an improvement. It can help to get a better disc with less work.