Study On Mechanical Behavior Of Connecting Bolt Of Wheel Forged Brake Disc For High Speed Train

As an important connecting and fastening part,bolt plays an important role in the safety of the brake disc.Its reliability and fatigue strength have a direct i MPact on the reliability of the train braking system and the safety of the train operation,so it is necessary to study the bolt fracture behavior.Based on the finite element method and the thermal-mechanical coupling theory,this paper analyzes the influence of the thermal expansion coefficient of bolt material on the mechanical properties of bolt,and concludes that the large thermal expansion coefficient is helpful to reduce the stress amplitude and the axial force variation amplitude of material,and it is helpful to increase the fatigue life of bolt;Co MPared with six kinds of braking conditions,the maximum axial force of bolt is about 76 k N,and the initial pretension of 55 k N The force is increased by 21 k N,which is instructive for the design of bolts.Considering the complexity and variability of the force on the brake disc bolt,there is a high requirement for the manufacture and assembly process of the bolt.Therefore,the heat treatment technology and assembly technology of the bolt material of the brake disc are studied.Through the tempering and tempering treatment test of a medium carbon Cr-Mo alloy structural steel and a low carbon Cr-Ni-W alloy structural steel,the appropriate heat treatment process is obtained.Through the research of the bolt assembly technology of brake disc,the tightening sequence,lubrication mode and tightening speed of the brake disc assembly fasteners are determined,and the optimal tightening parameters of the angle method are determined.The results show that the axial force dispersion of bolts is smaller and the assembly performance is better when the angle method is tightened.Based on the analysis of the basic principle of bolt connection,based on vdi2230 standard,the service state and load of wheel mounted brake disc in operation and braking process are analyzed and calculated and checked in parallel,the maximum and minimum pre tightening force range of bolt is obtained,and the tightening torque design range is calculated according to the actual torque coefficient test results;the safety coefficient of bolt is used It can be concluded that all safety factors meet the design requirements.This method provides the design idea and method for the brake disc fastener design,and has an important guiding significance for the brake disc fastener verification.This paper puts forward optimization suggestions for brake disc bolts.Firstly,the influence of the stiffness of equal rod bolt and thin rod bolt on the force of bolt connection system is analyzed,and then the difference between mj16 thread and M16 thread is analyzed.In order to co MPare the mechanical properties of mj16 bolt and M16 bolt,the simulation analysis is carried out based on the finite element method,and the advantages and disadvantages of their mechanical properties are comprehensively analyzed The fatigue life of the two kinds of bolts was tested by fatigue testing machine.By co MParing the results of theoretical calculation and test data,it was verified that the mechanical properties of mj16 bolt were greatly and comprehensively improved co MPared with M16 bolt,the thread stress of mj16 bolt was more uniform,and the fatigue life was also much better than M16 bolt.