Simulation And Experimental Research On Ultrasonic Rolling Strengthening Of High-Speed Train Brake Disc

The brake disc is the core component of the basic brake system of the land high-speed vehicle.The damage failures such as friction loss and fatigue cracks generated during the service of high-speed train brake discs greatly reduce the braking reliability of the brake system and affect train operation safety.Therefore,it is imperative to further improve the wear resistance and stability of brake disc.The use of ultrasonic rolling technology to strengthen the friction surface of the brake disc and to achieve the modification of the surface mechanical properties is of great significance for improving the service life of the brake disc.The thesis uses a combination of simulation and experiment to carry out relevant research.The specific work and results were as follows:(1)Using the nonlinear dynamics software ANSYS / LS-DYNA,the macro simplified finite element model of the brake disc ultrasonic rolling was established.The influence of static pressure and impact times on the strengthening effect of brake disc was studied.The distribution of equivalent stress field in the impact area and the severity of plastic deformation of the surface layer were studied and analyzed.The distribution of the residual pressure stress in the depth direction of the brake disc was studied and analyzed,and compared with the test value,the validity of the macro simulation was verified.The evolution of the surface profile of the brake disc and the relationship between the depth of the impact crater and the static pressure and the impact times were studied and analyzed.In order to obtain the factors affecting the surface hardness and wear resistance of the brake disc,the equivalent strain of the brake disc was studied and analyzed to characterize the working hardening effect of the brake disc.(2)Using the MICROSTRUCTURE module of DEFORM-3D software,the microstructure morphology evolution of the surface layer of the brake disc during ultrasonic rolling was studied and analyzed.The effects of dislocation density,grain boundary and grain size on the microstructure of brake disc materials were studied and analyzed.The distribution of the grain refinement along the depth of the brake disc was studied and analyzed,compared with the microstructure distribution of the test surface layer,the validity of the micro simulation was verified.The microstructure simulation analysis can better explain the macro deformation rule of brake disc specimen and the grain refinement mechanism of ultrasonic rolling.(3)Using Hawking Ultrasonic Strengthening Equipment to design the brake disk ultrasonic rolling strengthening test program.The strengthening effect of the brake disc before and after ultrasonic rolling was studied and compared by using a variety of surface performance measuring equipment.The effect laws of static pressure,rolling times and cross feed parameters on surface roughness,residual stress and surface hardness were studied and analyzed.Scanning electron microscope(SEM)was used to study and analyze the evolution law of microstructure morphology of the deformation layer on the surface of the brake disc.The influence of static pressure and rolling times on the surface microstructure of the brake disc in the direction of depth was observed by taking the refinement layer as the index.The mechanism of ultrasonic rolling strengthening of brake disc was studied from the microcosmic point of view.The simulation and experiment in this paper were from macro analysis to micro-structure morphology analysis of the research ideas.The results show that,the ultrasonic rolling process can achieve the modification and strengthening effect required by the brake disc materials of the high-speed trains in service.Furthermore,the comprehensive mechanical properties of the brake disc material were improved,the service life of the brake disc was prolonged,and the braking safety was increased.