Research On Fatigue Failure Of Grooved Brake Disc Affected By Thermo Mechanical Coupling

As a deceleration and shutdown device for large high-speed heavy-duty mechanical equipment,disc brakes are the key components to ensure the safe operation of equipment.The brake disc is an important part of the disc brake,and its performance has an important impact on the brake efficiency and reliability of the brake.The groove structure changes the contact state of the friction interface by changing the surface geometry of the brake disc,thereby changing the vibration,noise,and friction factor during the braking process.At present,more and more applications have been applied to the high-speed heavy-load disc type.In the brake.Fatigue failure is one of the main failure forms of brake discs.In order to ensure the safe operation of high-speed and heavy-load brake discs,it is necessary to calculate and analyze the fatigue life of grooved brake discs.In this paper,the thermal-mechanical coupled finite element simulation model of the brake disc is first established and verified.Then,the temperature stress of the grooved brake disc during the braking process of the thermal-mechanical coupling simulation is used as the analysis condition of fatigue failure.The fatigue failure theory and fracture mechanics theory are used to analyze the crack initiation and crack propagation of the grooved brake disc,and the influence rule of the groove on the fatigue failure of the brake disc is obtained.The main research contents and results are as follows:(1)The brake principle and process of disc brake are analyzed.According to the contact theory and heat conduction theory in the process of thermo mechanical coupling,the heat conduction equation,the boundary conditions of heat conduction and heat convection of the grooved disc brake are analyzed,and the influence of temperature on the material parameters is considered.The finite element model of the grooved disc brake is established.Based on the existing experimental data of disc brake,the thermal mechanical coupling simulation model of brake disc is verified.Then the validity of the finite element model is determined.(2)The results of thermal mechanical coupling simulation of grooved brake disc are analyzed,and the influence rule of groove shape on the temperature and stress of brake disc in the process of braking is obtained,and the reason of this rule is analyzed.Based on the results of thermo mechanical coupling simulation,the crack initiation life and location of the grooved brake disc are calculated by Fe safe software.Combined with the results of thermo mechanical coupling analysis,the influence of groove shape on the crack initiation of the grooved brake disc is analyzed.(3)Based on the temperature stress in the crack initiation region of the grooved brake disc,a simplified model of the crack propagation of the grooved brake disc is established by the theory of fracture mechanics.The crack propagation life of the grooved brake disc is calculated by the software FRANC3 D,and the influence rule of the groove shape on the crack propagation life of the brake disc is obtained.(4)The crack growth model with groove is established,and the finite element simulation is carried out by the maximum principal stress method and XFEM.The influence of groove angle on the crack growth process and crack growth path is studied.The results show that the stress state near the groove changes,which leads to two results.When the crack propagates near the groove,it tends to propagate perpendicular to the groove;when the groove angle is large,the crack will appear discontinuity near the groove.Above all,this paper mainly studies the influence of different groove sizes on the fatigue life of the groove type brake disc,which provides the basis for the selection and optimization of the groove type brake disc in the future.