Analysis Of Dynamic Characteristics Of Frictional Vibration Of Axial Brake Disc

With the rapid development of the high-speed rail,high-speed rails have become the mainstream instead of traditional passenger trains.The operating speed of high-speed trains continues to increase.At present,the high-speed rails are mostly operated at the speed of 300km/h and 200km/h.Trains are required to have a stable and reliable braking system due to the high speed.The basic braking device of most of the high-speed trains is disc brakes.However,the principle of disc brakes is by dry friction between brake pads and brake disc.During braking,high frequency friction will inevitably cause vibration accompanying braking noise and thermal fatigue at the same time.The brake disc is subjected to a complicated load in the braking process,which affects the reliability of the bolt connection.The research on brake squeal noise is in-depth study at home and abroad.It is often accepted that the modal coupling theory is the source of friction squeal noise.Because frictional vibration and noise are inextricably linked,based on the modal coupling theory,this paper establishes the finite element model of the axle disc brake system and considers the boundary conditions and geometric constraints among the components of the braking system according to the real situation.In this thesis,frequency domain analysis is performed by complex eigenvalue method and time-domain response analysis is performed by transient dynamic method to study the friction and vibration of braking system.Simulation results show that:(1)As the friction coefficient increases from small to large,the number of unstable modalities gradually increases,and lower-order modalities are more easily excited.The friction coefficient continues to increase,with the results that the unstable modes will not continue to increase,but the real part of the complex eigenvalue corresponding to the same mode will increase,reflecting that the braking system is more prone to self-excited vibration.The real part of the eigenvalue increases significantly with the increase of the elastic modulus of the brake lining,which indicates that the tendency of the system to generate frictional vibration increases.The real part of the characteristic value decreases with the increase of the elastic modulus of the brake disc,indicating that the tendency of the system to generate frictional vibration is reduced.(2)The transient dynamics method is used for braking system acceleration parameters such as time domain response,frequency composition brake friction area is relatively complex and parameter analysis found that the friction coefficient increases makes friction vibration amplitude increase,but have less effect on friction vibration main frequency.The increase of elastic modulus of brake disc obviously increases the main frequency of vibration.Brake pressure and rotational speed have different degrees of influence on friction vibration.(3)According to the simulation cloud map under long-downhill conditions,locates the larger stress on the brake disk,hub and bolt,and then extract the location of the stress time history and get the process of friction vibration stress change rule so as to proof pre-tightening force to reduce vibration amplitude.