| The vehicles have entered into ordinary people's family and given more convenience to people's life and work with the rapid development of Chinese automobile industry. Customer's expectation on safety and comfort are rapidly catching the world class level. Vehicle noise, in particular the brake noise can distract people's attention and make people fidgeted, so it has increasingly attracted widespread attention of customers. The study of the mechanism of brake noise and how to reduce noise are essential.Brake noise hazards are mainly manifested in the following aspects:1.Community environment noise makes community residents'complaint;2.Affecting driver's comfort and causing customer dissatisfaction;3.Affecting resource input of the design and manufacture of disk brake assembly;4.Affecting suppliers'product development of disk brake assembly;5.Affecting the sale of automobile plants.So, finding the root cause of brake noise and designing a kind of low-noise disk brake assembly, whether from reducing noise pollution, meeting customers'demands and improving product development of disk brake assembly or raising the sales level of automobile plants are very meaningful.Disk brakes and drum brakes are two major types of brakes. disk brakes has these advantages such as:thermal stabilization,enhydrous stabilization and easiness in changing or servicing the disk brakes,so we can see that disk brakes has considerable market prospect. This paper aim at the configuration of diskbrake assembly, to change the parameters of disk brake,brake flake and metal band can optimize the disk brake assembly, to use mode analysis can put forward some measures of reducing noise and validate the validity of measures.First, a summary of previous study on brake noise is presented to focusing on brake noise research methodology and major achievements. The unexplored area has also been mentioned. The focus area of noise is identified from 500Hz to 1000Hz. Then the basal essence and steps of FEM are introduced,the function,modules and steps of Pro/E and ANSYS are expatiated.Statics model of the disk brake assembly must be established, reasonable simulation restrictions and boundary conditions and loads must be ascertained before its three-dimensional model and FEM model is established.The schematic figure of statics model is showed as figure 1:The following work can be done based on statics model of the disk brake assembly. First, the three-dimensional models of brake disk and brake flake and metal band are established by using Pro/E,then their FEM models are made by using ANSYS. The reason that the three-dimensional models of disk brake assembly are established in Pro/E is that ANSYS has powerful analysis functionbut its modeling function is weak, so we can use Pro/E to establish models and transfer the models to ANSYS, it's convenient and we can save much time. Establishing FEM models of the disk brake assembly is critical in model analysis, and it's a complicated work that the models need be modified in the process of modeling FEM models of the disk brake assembly in order to acquire logical gridding. The material parameters of modeling the FEM models is shown in chart 1.The main purpose of FEM is to check influence of the configuration under certain loads. So it's very critical to make reasonable loads in FEM. The CA7220 car is given an example to ascertain the value of loads. Loads of the single wheel are shown in figure 2. A point which needs to be mentioned is that the result loads are critical loads, because brake disk and brake flake hold each other when the loads exceed the critical loads, and the friction noise of wheel and ground is produced in this condition. The type and value of result loads is shown as follow: M = 1352.48N P = 3.17MP In above equation, M is torque of disk brake, P is pressure of disk brake.Model analysis is carried out after the theory of model analysis and its steps are introduced by using ANSYS. We can find that the intrinsic frequencies of brake disk and brake flake and metal band in the range of 500Hz-1000Hz are close in certain model after we analyse the values of intrinsic frequencies of each rank, so we think this range is analysis emphasis. Improved methods are put forward based on model analysis as follow:1.Increasing the thickness of brake disk and drilling holes in the brake disk can increase the intrinsic frequency of brake disk and avoid the range of 500 Hz-1000Hz;2.The vibration frequency of brake flake is more higher than the vibration frequency of brake disk and metal band, considering the material particularity of brake flake, we can only change the thickness of brake flake and make its vibration frequency increase over 1000Hz, so the amplitude descends and the aim of reducing noise comes true;3.Changing the thickness and PREX of metal band can increase its vibration frequency and avoid the frequency range of making noise and achieve the purposeof reducing noise.Models of the disk brake assembly are reconstructed in Pro/E based on above improved methods, then transfer these models to ANSYS and establish the FEM models and implement model analysis, the loads and restrictions are unchanged in this process. Comparing the vibration models and frequencies of parts which are acquired by model analysis to the value of un-optimized models and frequencies, we can draw a conclusion that above improved methods can achieve the purpose of reducing noise.Some assisted methods are put forward in order to achieve the purpose of reducing noise based on above improved methods, Such as: daubing some grease and lacquer in the joint of brake flake and metal band, applying the same area rubber or damping patch on the surface of metal band where the surface don't work and so on. These methods can reduce noise effectively.It has referential meaning that the brake disk assembly is applied to model analysis and the structures are optimized as well as the calculated result and the conclusion are used to estimate vibration noise of the brake disk assembly. The method of reducing noise of the brake disk assembly is needed to test further by experiment. |
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