Research On Destabilization Of Low-frequency Vibration Of Drum Brake

The purpose of this dissertation is mainly to study destabilization of low-frequency vibration of drum brake.The main works of it are as follows:1. Existing low-frequency vibration theories of drum brake are analyzed and the shortcomings in those theories are pointed out. They can not illustrate the relationship of friction coefficient and destabilization of low-frequency vibration of drum brake very well. As a result, a new model of low-frequency vibration of drum brake is proposed based on practical engineering conditions. The new vibration model is described as a set of constant-coefficient differential equations.2. The mechanism analysis of low-frequency vibration of drum brake is made for the new model. The relationship of friction coefficient and destabilization of low-frequency vibration is studied with stability theory. The major conclusions are as followers:Whether friction coefficient varies or not, destabilization of low-frequency vibration may always occur if friction coefficient is greater than critical value. When friction coefficient is becomes lower, however, this kind of destabilization may still occur under certain conditions. 3. A new optimization model is proposed. If friction coefficient is constant which is greater than critical value, while stiffness and angle of drum brake is lower than critical value, destabilization of low-frequency vibration will take place. In order to refrain from this condition, the structural parameter of drum brake is optimized with the method of genetic algorithm. After optimization, braking efficiency increases largely, and the most important is that destabilization of low-frequency vibration of drum brake is prevented efficiently. It also illustrates that reasonable structural parameter of drum brake can avoid destabilization when friction coefficient is overgreat.4. Modal analysis of parts of drum brake is accomplished with Finite Element Method. As the frequency of2nd rank of brake shoe approximates to the one of five-order of plate, destabilization of low-frequency vibration may happen. The major conclusion is that unreasonable structural parameter of drum brake may give rise to destabilization.